Check out www.PESinsight.com. It talks about features in PES3 but that should be the same for WE7 International.
there are even few new animation i heard, and i know that there is a new "trick" with the ball if u move up and down the right analogic stick. there are even 2 new licensed teams , Juventus (with the 2003/2004 kit) and Feyenord(2003/2004 ? ) and the we7 licensed team (parma , milan, lazio, roma , all with the 2002/2003 kits) about the gameplay i got the feeling that pes3 is easier, less frustrating, because in we7 it was like all the teams played catenaccio, so there were often like 8 players in the box when u attacked, while pes3 is maybe more realistic, there are more spaces to break through
I strongly suggest u to buy (if u dont have a ps2) a ps2 joypad and a convertor like : PSX Joy Converter USB or PSX Super Joybox