I'd say go for the Volos... or rather the newer Volo Power fins (or Volo Race if you prefer full-foot fins) ... what's the difference between the original Volos and the Volo Power? The original Volos had a few problems with some batches breaking at the hinge. The Volo Power tries to solve this by extending the center V-channel all the way up, close to the foot pocket... reinforcing the hinge area a bit.
I have the Volo Race fins (full-foot) ... and recently switched to the ever reliable Jetfins. Despite all the hype of the Jets, I did find that they are slower than my Volos when using the flutter kick. I can go fast with Jets... but not as fast as with the Volos. Frog kicks with the Volos however is another story, although faster than most other fins out there, they are much slower than the Jets when using the frog-kick. And forget about reverse frogs or other weird kicks on the Volos. They are much too soft. But I have to admit, Mares' hinge and channel thrust technology is very evident with the Volo... I can sustain higher speeds much longer on them than with any other fin I've tried... and mind you, I'm biased towards Jets now that I'm preping to take my DIR-F class.