Ricky Tinez just did a fairly in depth demo on youtube that’s worth checking out. I’ll put the link here. Overall, it sounds pretty amazing and I like the semitone tuning. Obviously the design is a little different, but that’s more a matter of preference. I also like the choke input, and in the video it’s used to make some cool sounding musical phrases.
I think the controls on rings are a bit better than the ones on Surface (but admittedly that could be because I’m more used to rings). The single biggest “downside” in the Rings v Surface discussion is that Surface does not have an audio input. Obviously, Rings sounds beautiful on it’s own, but you can get so much more by running other oscillators, contact mics, noise, whatever, through the intput. Surface won’t have any of that.
My takeaway was that Surface is a solid choice for people that see videos of rings and just like that rings sound and want to use it in their rack. It’s smaller, has the choke controls, and (by my estimation) has a few extra mode to dial in the sound you want. But if you actually want the resonator and extra features there, rings is still kings.