Quick review of the ZTs:

301 = beast! This feels GREAT and as if it'll take any abuse you'd give it. It is, however, a BIG knife. It's also heavy. I'm worried sharpening a recurve edge will be difficult. LOVE the assisted opening.

350 = my least favorite for "feel". It is lighter and smaller than the 301, but not enough to justify the weight. Feels "cheaper" too. Recurve and assisted opening same as the 301.

550 = HARD TO OPEN! It's tight and no flipper. I opened it about 100 times and it's smoothing out to feel like it's on bearings. Super quality knife. If it had a flipper I'd rate this very highly.

561 = Surprisingly light for its size. Feels great in the hand. A little hard to open (will it smooth out / wear in)? Nice blade size and profile, but this is a BIG pocket knife.

At this time all I've done is handle them. Based upon initial impressions, my order of preference (favorite to least favorite):

301
561
350
550

JYD #123 The great one formerly known as Architect.

I am now a fictional British television police officer (currently a Detective Sgt) at Thames Valley Station. My governor is Detective Inspector Fred Thursday and it’s 1969.