That would depend on how you use them... Vinyl degrades with use (although
I have heard of a LASER stylused turntable which doesn't damage the vinyl
at all!!! but it costs $10,000 :( !!!!)
CDs on the other hand degrade with age... therefore all your CDs will sound
crappy in @ 15 years... some investment eh? Although it would make sense
from a label's point of view because they get to sell you the same product
over again if you want to hear it again. I hope that answered your
question.
Peace,
Lo-Ki
(listening to a record pressed in 1970 and loving the sound quality on my
"too expensive" technics sl1200 turntable.)