They're both excellent knives that look and perform great. Between the two, I would guess I end up carrying the 0566 a little bit more. While I do like the aesthetics of the 0770 more, the 0566 does handle a little bit better for me. This is all highly subjective and a matter of personal preference though.
Some comparisons/contrasts between the two:
- Blade: Both use Elmax (although the 0770 does have M390 and M4 variants now) and have the same blade stock thickness (0.121"). The 0566 has a bit more steel at the tip, so it should be stronger. The 0770 has a higher grind, so it will be a better slicer. The 0566 is a traditional drop point with a good length of straight edge and a bit of a belly, whereas the 0770 is more a sheepsfoot with a slight curve along the entire cutting edge. The 0566 feels better when cutting in with a bit of weight towards the middle of the blade, whereas the 0770 offers a bit better tip control.
- Handle: The 0566 uses G10, versus carbon fiber or aluminum for the 0770. The G10 is textured and will provide better grip. The CF and aluminum handles on the 0770 aren't perfectly smooth though. It has a light texture not unlike very high grit sandpaper (2000, or maybe higher). The handle on the 0566 is a bit longer. Both have solid ergos (no significant hotspots), although if you are going to be doing a lot of cutting, the larger handle might be an advantage.
- Carrying: The 0566 has a quad-position deep carry clip, versus the 0770 has a reversible clip for tip-up carry on left or right sides. The 0770 has a smaller footprint and is thinner, so it does carry more comfortably.
- Opening/Closing: Both are assisted opening flippers. The 0770CF does have a bit of jimping on the flipper that gives a nice bit of extra traction. The 0566 can be de-assisted (is drilled with a detent hole), although I tried it and opted to put the torsion bar back in (just personal preference). I haven't taken my 0770CF apart, so I don't know if it is drilled with a detent hole.
- Lock: 0566 is a frame lock, and 0770 is a liner lock. Both lock up plenty solid.
What knives do you have experience with, and what do you like (or dislike) about them?