They'd be the same as any other recordings of the period, with the caveat that if the original masters don't exist anymore or are damaged, then you have to take whatever tapes you still have on hand, with the generation loss that entails.
Some certainly do sound better than others. I've often wondered what they were thinking when they compressed and EQd all the "Pirates" tracks so harshly. Maybe they were compensating for the speaker technology of the time?
I've only gotten a chance to give a close listen to disc 1 so far. I am impressed overall. I heard one minor mix mistake in the Tiki Room (which I'll keep to myself, since you'd probably never notice it without headphones anyway). Otherwise, everything sounds fabulous given the obvious limitations of the source material. The care Randy and company have put into it really shows.
There's digital stereo "ambiance" added to most of the mono recordings. Ordinarily I get very bent out of shape about this kind of thing, but in this case the stated purpose is to recreate the actual atmosphere of being in the attraction rather than to do a faithful reissue of a previously available recording. And it does that quite well.
I had my doubts about the crossfaded "day at the park" concept, but I'm over them. It really is a wonderful set, great fun to listen to. If you don't have yours yet, get off your butt and make that call.