I prefer the handle shape of the 640/740 series knives, but I understand that they're discontinued. I'm less keen on the handle on the 511 and I don't think I've seen a 510. I really dislike the handles on the bushcraft range - that finger groove does nothing for me at all.
The best bet for me is the clipper or the craftline handles, and these knives are easily available, and cheap.
I really like the 106 and 120 sloyd knives, but they're better suited to woodcarving rather than general use.
Bottom line is as the others have said - go for the one that you like the look of. They are excellent value for money.
(Oh, I see you are in West Yorkshire.
Clas Ohlson in Leeds should stock them.)
Cheers