It all depends... many collectors will often "buy by the flag", meaning if the band is from the UK, they'll get the album from the UK. This was probably more of an issue in the days when the LP was the predominant format, going on the presumption that the master tape was used for LP in the country of origin, and a backup, or copy, or later generation tape was sent overseas for other pressings. These days, with digital, the issue might be more about who mastered the disc and where and how it's being produced. I know there are people that assert the UK 4AD CDs of Dead Can Dance are superior to the US versions. I bought the UK version of one when I was there based on this, but, I haven't had a chance to compare it to a US one. Quite often, I've purchased Japanese versions of Jazz CDs because the mastering and production were indeed far superior to the US counterparts. If you seek info about specific CDs and which versions are most highly recommended, there is plenty of discussion over at the Steve Hoffman forums:

http://www.stevehoffman.tv/forums/