They are all good knives, it's mostly minor differences. The Ritter blade profile is a better slicer than the 551, about equal to the 550. The pointy tip on the 551 is better for picking splinters and thorns out with. I am in the minority, but I don't like Benchmade's S30V steel. Too chippy in my experience. YMMV... FWIW the black coating on the few coated Grips I've had has worn pretty quickly, the plain blades don't show the scuffs as much.