Funny enough, I thought Arrow was going to beat Flash out (season 1) when he was going around being Batman; even going as far as actually killing his enemies...then they made him a boyscout; subduing villains instead of killing them, and the forced League of Assassins story arch just made me hate everything about it and made me like Flash more. Zoom kicking Flash's ass every other scene was actually surprising to see. The writers actually kept it true to the comics and it was a far more enjoyable show (sanz love affairs/triangles).
While the better actors are in Arrow, I prefer Flash so far.