I say if you're looking at specific maps, look at Badlands (of course), Process, Snakewater, Granary, and Gullywash...
of course, each one of these maps has its faults. Snakewater and Gullywash have very difficult to push lasts and tend to stalemate, where Granary has bugs and asymmetry issues.
If you're making maps, like I am, be sure to only take some inspiration from these maps, because you don't want to make maps that are practically the same as other maps but worse (read: follower).
Generally, 5CP is the gamemode to go for, as A/D CP and KOTH aren't really prime places for testing - from experience, A/D doesn't get tested barely at all b/c people don't like to scrim those maps, and KOTH is generally either a love/hate relationship for each map. 5CP offers better testing because feedback will be different for each point, and testing will probably be better.
If ya want help making maps, just add me on steam - I've had some experience with mapping for comp so I'd be willing to help.
My two cents. I'll be willing to go more in-depth in later posts or if conversation becomes heated.