from what I've read and seen in the subaru shop I worked at the internals on the 2.2t are stronger. Not only that but since there is less stroke there is also less stress on the reciprocating assembly. Either way you go you'll want to replace the pistons as I believe they are cast aluminum in both cases. I'm not sure the price but you could consider getting a crawford closed deck 2.5 if you want something bombproof, well bomb resistant. I have seen a 2.5 block with 25psi crack a cylinder because of stress on the open block.
the big question is are you going to have enough power for it to matter either way?unless it's a drag car I personally wouldn't want more than 300whp, but then again I'm cheap and like my stuff to last and be streetable.