what is the difference on 2ZR-FE engines?

[SirDigby]

hello, I just purchased a yaris! I've been doing some research on what needs to be done for faster driving. i'm a big fan of rotrex superchargers, but I have not found anything on here about anyone using one on the 1nz, but I've found kits in japan. i'm not interested in a blitz s/c because the efficiency is not there on the screw s/c imo. I've seen a few turbo kits, and they seem to work well. I came across the engine swap posts, but they were pretty vague and there seemed to be just a bunch of talk.
so, the 2zr-fe seems to be a good swap. the issue I have is all posts say XD is the swap, but it has the lowest output numbers. what is the difference between XD and corolla 2ZR-FE? is it just exhaust manifold and other bolt-ons, or is the block physically different? I see there is a 10hp-ish gain from going with a corolla engine. why is the XD pushed so much when it's the weakest output?
thanks for any info.
j.