The Fuse is possibly my favorite mid now. Has tons of glide, pretty neutral in stability, really locks onto lines well if you don't OAT or overpower it. My Opto is beat where dead straight is as easy as a hyzer flip and it holds an anny very well still. It's an excellent complement to the Buzzz, basically the closest thing to a Comet in a beadless package there is.
My 170 Opto River flies like a Star Eagle in its sweet spot or really beat. Easy to turn, easy to S-curve, still fades a little and mostly forward at that which ekes out all the more distance. Glides like a hovercraft. When new it flew a bit like beat Teebird or Leopard maybe. It definitely sails though.
I was not impressed with the Core. It has a fairly thin rim that feels awkward to me. If you throw it flat, it can really go with nice accuracy. But if it tilts much from flat either way it drops like a stone, especially with anhyzers, won't hold a moderate anny for a damn. Core < Buzzz/Roc in my opinion.