1.02 is fine for STW-WE/MI SP. I like it better than the original stat because cav are much better. Some don't like the power of guns, but I never have a problem with them (because I usually finish the game well before they come into play much).

Original STW is a classic that many people still enjoy. I think it's a bit more challenging because it takes twice as long and costs twice as much to build most things. On the other hand, I really like that WE-MI has several different campaigns that you can play: 1530, 1550, 1580 and the Mongol Invasion, in addition to the classic Sengoku Jidai. For that reason alone I'd recommend WE-MI, patched to 1.02.

1.03 was made primarily to improve WE-MI MP. Still, I think it would yield a nice SP campaign as well. Just an extra step though really.

If you get a swapper you can play whatever patch you want, changing on the fly as you like. Check the STW MP thread for a link. Remember that, if you do get the swapper, you need to install the official 1.02 beta first. Get that at the .com download site.