Depends how good the MDMA is in each case really. Poor quality pills are not as good as better quality powder/xtal and vice versa. I prefer xtal myself but that's probably just cos I've had far more of it than of pills. I like a good pill too. It's the 'good' bit which is key.
I've also heard plenty people claim that pills are somehow more euphoric. This is just plain silly. Some pills are godawful things and some are divine. I personally always found xtal more reliable in terms of quality but that was before I knew about things like Pill Reports, BL and test kits. At the risk of stating the obvious, MDMA is MDMA and it's the quality of the synth that is what makes the difference. That and set & setting obviously.
Also, some pills have active cuts (speed or maybe caffeine and the like) so those ones would probably have more kick than xtal or powder... not that the latter is any type of proof of quality cos you can add cut to anything.
EDIT: What House said only with extraneous words and stuff.