I have the Supraphon LP in front of me writing this, but perversely haven't had my record player connected to my system for 15 years. I also have the P P CD and cannot remember anything besides liking it. An astounding work and Obrecht probably (?) the most underrecorded polyphonist of them all (Isaac also comes to mind).
Does the LP sleeve say what the scale of it is? Do they use instruments? Big choir or small?
This is such an important piece I think -- the Peter Philips recording is very satisfactory too. On amazon you'll read complaining reviews which say that it's boring music, but I think it's full of major events, and has a rigour which, as always with Obrecht, makes me think of composers like J S Bach and Ludwig van Beethoven. If you're not dependent on music stuffed with tunes you can hum and rhythms you can tap your feet to, then I think you'll be bowled over by the mass. And someone complains that The Tallis Singers are too cold and too risk-averse, but I think that's nonsense.