Arrow is nowhere near as good as Gotham at its best. Or worst, actually, since Arrow is basically unwatchable. The Berlanti shows are some of the worst written, worst produced on tv. When they're good, it's mainly only because of the cast being strong enough to save the material (which the Arrow cast simply isn't strong enough to do). And even the best of the Berlanti shows (the Flash) is often dragged down by idiotic plotting, bad writing and wildly inconsistent characterization (yes, worse than Gotham's, sometimes).
At least Gotham looks nice and has some great drama among the wackiness (like Bruce/Alfred, Gordon/Bullock, etc). The Berlanti shows try to subsist exclusively on colorful action (which only the Flash actually even manages to do well) and terrible romance/soap opera drama (which none of them do well).