I thought I typed up a post here about the new remasters but apparently not. I’ve heard almost all of them on vinyl, I’m assuming the CDs will be very similar (maybe just slightly more compressed). If that’s the case, here is what I recommend (in order of priority):
Dance of Death - Not heavily distorted the way the original was. That awful crunch is gone and the music breathes a bit more. The album is finally listenable.
Fear of the Dark - better than the original CD release. I haven’t heard the 98 version but knowing the general quality of those remasters, it’s probably better than that one too.
X Factor/Virtual XI - These albums obviously had a lot of mixing problems which aren’t fixed here, but the mastering is slightly better. They’re a bit more balanced and Virtual XI isn’t as brick walled.
The other reunion albums are fine, definitely a slight improvement but I doubt most people will be able to tell the difference. The original mastering on those albums is fine anyway. No Prayer on vinyl was a bit compressed so I would stay away from it if you have the original CD. Same goes for the 80s albums, they were a bit more inconsistent in quality. That being said, if all you have are the CDs released in 1998, these new ones would probably be an improvement (especially SIT and Seventh Son). Of course you can also just download them right now on iTunes.