2002 is arguably as good as 98, and many fans like it better because of the roster. I've always preferred the vanilla versions of both games, as I've felt the updated versions were a little slapdash and I hate the presentation updates. The UM versions have larger rosters than the vanilla releases, if those characters are important to you. I feel the balance is a bit better in the Vanilla releases, though.
Also, the UM version of 2002 does NOT have K9999. Not that K9999 is a great character, but the homage (clone) of Tetsuo from Akira has always been a nice touch.
In 2K2UM they've mutilated his sprite and turned him into a broken mess of a character both in design and mechanics to skirt any legal issues.
There isn't anything like playing Neo games on Neo hardware, and if you prefer vanilla 98, you'll most likely prefer vanilla 2002. 98 is hands down my favorite competitive fighting game, but 2002 is no slouch. If you like 98, you're pretty much guaranteed to enjoy 2002 as well.