I echo what Pitts2112 is saying. If you've never flown different aerobatics planes, don't buy one based on the advice here.
The other thing you might want to consider is whether you want a pure aerobatics plane, or want some or a lot of touring capabilities in it as well.
Me, I fly the clubs Robin 2160. Mostly because nothing else is available to do aerobatics. It doesn't have a constant speed prop, doesn't have an inverted flight system but is fine for basic aerobatics competitions, and can even, if flown competently, compete in the standard class. Higher than that, forget it. But at the same time it's also a very decent tourer and a very benign aircraft for low-time pilots: side by side seating, nosewheel, GPS, VOR and a four-hour endurance.
I have never flown one, but I heard the Decathlon has more or less the same qualities.
Going up the scale is probably the CAP-10. Still a decent tourer but it does have an inverted flight system and I think a constant speed prop as well (not sure though). And it's a taildragger of course.
Higher up the scale you get aircraft that are excellent at aerobatics, like the Pitts, Extras, CAP-21, Yak and so forth. But as single-purpose aerobatics planes, they are less suitable for other purposes, because they have very limited range/endurance, are solo only or have virtually no baggage space.
Oh, and if you get one of those specialized aerobatics planes, you'd better make sure your friends are into heavy aerobatics too, otherwise they won't get much use out of such a plane.
My advice: rent for at least a year or so until you have sorted out what type of flying you like to do most. Serious touring (possibly IFR/IMC/Night), bimbling about/200 euro lunches, aerobatics, formation flying? Then start hiring different types of planes that suit that style of flying so you know what's available. And only then start thinking about the exact type of plane you want to buy, and with whom.
Right now, in automotive terms, you're asking us to choose between a VW Lupo (the Pioneer) or a Harley Davidson (the Pitts), and are hinting at other options as well. They each have their good and bad points. How should we choose between them without knowing about your experience, budget and aspirations?