There are several threads here, and elsewhere, regarding the 2014 vinyl
releases. I think that Mothership on vinyl was mastered by the same guy
that did the 2014 releases on vinyl, but a lower rez digital transfer was the
basis for Mothership. (Mothership, as I recall, is sort of a 'best of,' at least
on vinyl and may not have all tracks you want).
The new vinyl (2014) is pretty good if you are only casually into Zep- the
pressings are quiet, and they aren't the kind of sterile, flat sounding digital
to vinyl sound that I think of as worst of the breed. But, if you are interested
in better sound for Zep on vinyl, there are myriad possibilities, most of them
older pressings. The Piros remasters done in the mid 70's are very good,
and don't command crazy prices. The trick, of course, is condition, and
that's where a lot of people are going to be satisfied with a fresh record
rather than hunting for old vinyl that was probably put through some serious
playing/abuse.
There are, of course, many far more expensive, collectible pressings of
these albums, but that's another story. (FWIW, i have quite a few different
pressings of Zep, and one of the best- of Zep 1- is a particular Piros
remaster from the mid-70's which holds its own- and in some ways betters-
many of the more collectible, expensive ones).
I can't comment on the hi-rez digital formats, cause I don't use them.
At bottom, I personally don't consider any of the Zep catalog to be
'audiophile' quality sound, so it really is about finding the best sound given
the limitations of the original recordings.
Good luck.