My initial acro training was in a 115hp Grob. It works fine, but you spend a fair amount of time diving for speed then climbing back up after the manouevre. But when you're starting that's not so bad, it gives you time to think about what went wrong!
After that I moved to a 180hp Decathlon which seemed MUCH better and you spend relatively little time climbing back up again. I've once flown acro in a Citabria, but it was one of the more powerful variants (160hp I think). You work HARD to do acro in a Citabria, that I can tell you... lots of stick force involved and things take a long time to happen. In terms of airframe strength, it's fully aerobatic, but as a serious aerobatic plane it's pretty marginal. But to get started, it'll be fine. Just make sure you're not in a position to transition to a Pitts later on, as that is VERY bad for your wallet.
Recently I've had the chance to fly acro in a T6 (Harvard) and that's not terribly different from a Citabria, both stick forces and time to make things happen. (The bill is rather larger though).
n5296s