Specifically:
Diva has greatly musical components ... not so many knobs but very, very good ones. The analog modeling is technically advanced, but it's also based on some synths with great sonic reputations and developed by people who know what that comes from. I'm really surprised at how often and well this translates into getting something that sounds 'right', and just fits into a mix, as far as I've found opportunities to push that so far.
ACE still stands out with a clean, smooth transparency that is sort of coming from the opposite side - it's a sandbox for developing the musical or aural dynamics in the context of a modular synth that overcomes digital disadvantages, but really isn't extremely interested in gaining analog advantages from specific synth models quite the way Diva does. So it's in a more idealized place sonically, and that's certainly a worthy alternative.
