Not to be confused with the episode name, it's time to compare these shows. Both shows have their merits but only one can be crowned king. It's speed versus skill in an epic (categorical) showdown! Spoilers ahead.
Oliver Queen was a selfish billionaire who was dating Laurel Lance while having an affair with her little sister, Sara. He gets marooned on the island Lian Yu after a cruise with his father and Sara. Sara is assumed dead and his father Robert kills himself to save Oliver. Oliver is left with nothing but his wit (also Deathstroke, Shado and Canary) and trains himself to survive the island.
After returning to Starling City, Oliver feels obligated to save his city by murdering the corrupt leaders much like his father. He dons a cowl and becomes the Arrow. Oliver makes many sacrifices along the way to save his city and will do everything he can to protect the ones he loves.
Barry Allen was a kid who found that his weak stature caused him to constantly get into danger from bullies. Things get worse when his mother is murdered by a man in yellow lightning and his father is framed for the crime. Barry grows up with everyone not believing what he saw and dedicates his life to finding the man who murdered his mother.
When the Particle Accelerator in Central City is turned on, it causes a freak storm which causes a lightning bolt to strike Barry and put him in a coma for nine months. Barry wakes up with the ability to run at unfathomable speeds and teams up with the scientists at STAR Labs as The Flash to track down others who have gained abilities and prevent them from using their powers for evil.
You know, after three seasons I still feel like I can't trust Oliver. He just always sounds so emotionally distant, he doesn't make mistakes, he is always putting everyone else before him and makes the tough choices no one else will. It's kind of boring. Barry makes mistakes, he rebels against his team-mates, he screws up the timeline and also screws up his relationships. That's what makes him interesting, he isn't perfect, he's just like us except he has powers. He feels more reliant on his team-mates and he just seems more entertaining to watch.
Point: The Flash
The Love Interest
Felicity Smoak was an IT girl at Queen Consolidated who ran tech-based errands for Oliver without knowing the true intention. Eventually she finds out Oliver's identity and becomes an official member of Team Arrow. She develops feelings for Oliver and Oliver reciprocates them. The threat of being a vigilante is constantly putting conflict in the relationship but the two hope some day that they can work it out.
Iris West has been a friend of Barry since childhood. She was always supportive and loving to Barry and he developed a crush on her. Barry's obsession with finding his mother's killer has prevented them from being together and she is now dating Eddie Thawne. She is journalist who is always writing stories on The Flash without knowing that his true identity is her own best friend.
I'm not really cool with Iris being kept in the dark, there has been less and less reason for her to not know and now it just feels like a burden. Felicity almost knew right off the bat and that's what makes the relationship a lot more easier to develop. Granted I'm not a big fan of how they can never be together because Oliver has identity issues but it's a good thing she knows. Iris has to know some time.
John Diggle is a war veteran who lost his brother after an assassination from Deadshot. He eventually becomes the bodyguard of Oliver Queen and finds out his alter ego. He joins in his quest to save Starling City and hopes to some day come face to face with the people who hired Deadshot to kill his brother.
Laurel Lance is ex-girlfriend of Oliver Queen who, after the loss of her sister, became an alcoholic. Her job as a district attorney was on the line and the return of her sister seemed to make things worse. She eventually learns the identity of the [Arrow](series:720988) after Deathstroke reveals it. When her sister officially dies, she chooses to live on her legacy by becoming the Black Canary.
Roy Harper was a simple street thief until he robs Thea Queen, Oliver's sister. He develops a romantic relationship with her. His life is turned upside down when Deathstroke injects him with Mirakuru (basically the super solider serum of DC). He is eventually given the antidote by Oliver Queen and chooses to stand by him as Arsenal. Everyday, he tries to make emends for the crimes he has committed by being a vigilante.
Cisco Ramon is a scientist at STAR Labs who is unpopular and obsessed with pop culture. He finds a home at STAR Labs and assists Barry on his quest to take down evil meta-humans, often giving them witty names. He has a quick wit and is the comic relief of Team Flash.
Caitlyn Snow is another scientist at STAR Labs who loses her fiancé, Ronnie Raymond to the Particle Accelerator incident. She is more COLD (bazinga) than the rest of the team and is generally the moral compass. She also has a fun side to her. She is on a quest to save Ronnie after she discovers he has become a part of the FIRESTORM Matrix.
After Nora's death, Joe West adopts Barry and does his best to raise him. Joe is soon to discover Barry's identity as the Flash and joins him to stop the evil meta-humans. His top priority is to protect his daughter Iris West. He is an important father figure to Barry.
Maybe it's just the entertaining Cisco that's talking but I have to go with [The Flash](series:1068303). I've never that felt that Diggle has been that important to the team and Laurel's "sassyness" is a little obnoxious at times. Roy also hasn't really had proper time to develop. Give Diggle a costume already! Cisco is so much fun, I don't care if that's the major reason why I am giving the point.
Point: The Flash
Malcolm Merlyn had lost his wife after a brutal mugging and he has spent his life seeking revenge. He was trained by Ra's Al Ghul to be the ultimate killer and then manipulated the Queen family in initiating The Undertaking. A plan where Malcolm blows up the Glades, the Detroit of Starling City, to rid the city of evil. To get the plan to work, he kills Robert Queen by sabotaging the very boat that stranded Oliver on the island. Even after The Undertaking, he remains a threat to Team Arrow.
Eobard Thawne comes from the 25th century and develops super speed from unknown sources. He travels back in time and develops a grudge for The Flash and then travels back to when Barry was a kid to murder him. Barry prevents him and so he kills Nora Allen instead. Eobard gets stranded in the past from losing his abilities and seeks the help of Harrison Wells. He murders Harrison and his wife and then takes over his identity. As Harrison, he builds the Particle Accelerator to give Barry's powers quicker so that he can return to his own time. He has become a father figure to Barry and hides the secret that he is the man who killed his mother.
While a villain with super speed and from the future is cool, we still know very little about Eobard's past and at times it's tough to connect to his character when there's still years of back-story to cover. Malcolm is great, he believes what he is doing is right. Some of his actions can be justified with tragedy with the death of his wife and indirectly murdering his own son. He is now a broken man who is trying to hold on to the very few things that he cares about left. I'm sure when we finally know the history/future of the Flash feud we can grow a love for the character but he is still shrouded in mystery.
Parallels With The Comics
The name of the island that Oliver was stranded on in the comics was Starfish Island, really don't know why people change simple things such as names. That's why Ivy Pepper has bothered me so much on Gotham, just call her Pamela Isley! How hard is that? Felicity Smoak has remotely nothing in common with her comic book counterpart. While she is a lot more interesting, this is about the source material, not the quality of the changes. John Diggle isn't even a character from the comics and now when people are suggesting they make him John Stewart, it can't be done because the comics are the CW's b*tch and have made Diggle an official character.
The Flash is already alluding to Flashpoint and Infinite Crisis which are things that are about to become very big on the Flash. What makes the Flash so interesting is they seem to have a new character from the comics every episode. Basically everyone in the Flash is a character from the comics and all of them have had some slight hint to their comic book counterparts.
Point: The Flash
Bonus point to The Flash for special return roles from John Wesley Shipp, Amanda Pays and Mark Hamill.
With scores of 4 to 2, the Flash wins! While the Arrow has more interesting villains and better developed love interest, the Flash has a more entertaining hero and side characters, along with honour to the source material and even homages to the 1990s tv series.