Looking on Amazon, don't see the original versions available, looks like the remastered ones get high marks for improved sonics and the bonus songs anywave. If the extra bucks aren't an issue, the remasters look like the way to go. I have the originals.
It's a contest between The sky moves sideways and Coma Divine I'd say... Coma Divine wins it tho. Both of these are a bit more spacey with longer songs than your other PT disc's -- The difference between the styles of Stupid Dream and The Sky moves sideways is roughly the distance between Floyd's Wish you were here and Meddle (TSMS being roughly stylisticly similar to Meddle). Coma Divine is still spacey but not so much as TSMS.
Both are worthy albums and in the top tier of PT's catalog, from here you'll be moving into the second tier albums such as Lightbulb Sun, Up the Downstair, Stars Die which are the next ones to get. Natch, YMMV.
A new album is due in Febuary, with a tour to follow -- don't snooze and miss a chance to see em live!