the D3 from what ive heard is the most popular freediving watch there is. Its got a nice 1sec sample rate unlike most scuba watches so it catches even that last 4ft of the dive
i have a cressi EDY because i only wanted to get 1 watch to serve both purposes and i love it.
I assume that the freediving features are pretty much the same between the two..
since you already have a scuba wrist computer, i would say get whichever of the two you can find cheaper :P