Phenom x4 vs athlon x3?

First, I would never base a decision off unlocking a core, as it is probably 50/50 at best. So when deciding, say cache and an extra core, as that 4th core on the athlon is far from guaranteed. As for the cache, it depends on the app. Google athlon II reviews or benchmarks, and you should find plenty of good sites doing tests that answer your exact question (since the cachless (L3) models are much cheaper, everyone was wondering if performance was close enough back when they first came out).