I'd have to say for the first couple of years of my MDMA usage I definately preferred the 'fucked up' state. But time does change, since my tolerance has grown, and the magic has worn thin, I much prefer the more subtle clean peak.
A pure MDMA experience reveals the true nature of the drug in its most subtle ways. Purer forms just don't fuck you up so harshly, you feel much 'straighter'. You're able to do anything you feel like, you don't get the legless 'I'm too fucked to dance' feeling, nor do you get restless. The empathetic and love-enhancing qualities are much more noticably present rather than the forgetful off-chops lostness
Because of the subtlety it can often be said that purer forms don't hit you on the come on, but creep up on you, and hence you often can't be sure when you've actually come down.
The peak is longer and the side-effects are reduced. No extreme bruxism, no trouble sleeping, no head-aches, and generally a reduced level of emotional difficulty in the follow-up week.
Basically, the better the quality, the better the experience altogether. But, that said, because MDMA is such a subtle experience, its often hard for first-timers to get into it. If you focus your attention on how your body is 'feeling' or keep asking yourself 'is it doing anything?' then you'll find it hard to notice it - thats how subtle it is. You have to set about doing something and enjoying it, and soon you'll be engulfed in the peak. Thats why newcomers usually prefer the 'fucked up' state, its easy, and it does it all for you