I believe deca is a better muscle builder but I would go with test every time due to numerous reasons. Although there is no need to have to just pick one so go with both
I stack it with Test E and get great results. Deca builds quality muscle but it takes a while because it's a slow acting ester. Definitely part of my program.
I don't want to be "that guy" but deca is crap compared to NPP as recently discovered and "test is best" still holds true. Don't do a nandrolone without test unless you really don't care if you have sex for a while.
Take prami with nandrolones (and high dose tren) and get the best results. Keeps the prolactin in check.
In short, I would not run a nandrolone without test. I would not really run anything without test.