i'd go extigy...form all the reviews i've read, i've heard of no problems from the thing...
but that's only because i'm not too keen on the GTXP either...the breakout box doesnt' do anything for me, especially w/ it's nearly obsolete USB 1.1 ports (which is ok fi all u're using them for is joysticks or something) and an array of other connexions i'll never use...cept the headphone jack.
the extigy can be used standalone w/out a computer AFAIK as well...which might come in handy...looks nicer too.
personally i woudln't get either, but that's just me.