I took one of my 551s to a local sharp-thing emporium today and did the A-B-C comparison between it and both a new 560 and a 561. After a year, I actually like the stock G10 pattern on my 551 better than the 560 - or it's brown brother, the 561. All three had similar sized, although the cutting edge on the 551 was ~ 3/16" shorter, of similar thickness ElMax steel - and of similar sharpness, too. All could be thumbstud deployed, the newer 560/561 having the flipper deployment, too - an attribute to most. Not so important to me. My bushing pivot had most of a year of use behind it, making it slicker than the newer ball bearing 560/561. The final consideration... with a discount - and 10% S/T - you can't get a Happy Meal for the change left from three Benjamins. Each of my 551s was less than two Benjamins... and I already owned them. I left with my wallet intact. If you didn't get a 551 - get a 560/561. In my case, it would be needlessly copying what I already had.
Stainz