Overall quality wise how does spyderco Kershaw buck and benchmade compare to one another. What are each Ines strengths and weaknesses?
I personally feel Kershaw falls one small step below both Spyderco and Benchmade in terms of quality but Buck isn't even in the same world.
Here's how I see them....
Buck has a longer history and tradition of course, and many of us were handed down our father's or even grandfather's old buck knife. Nostalgia aside, the Buck knives made today are not of the same quality of materials nor are they designed with the same quality of ergonomics as the knives available from high-end manufacturers like Spyderco or Benchmade. The pricing of Buck knives is appropriately lower, and quality is quite good for the price, therefor they may be a good choice for many knife buyers who consider price a high priority.
Kershaw holds a place in the knife world somewhere between Buck and Spyderco / Benchmade. Kershaw is KAI USA and they also include ZT knives and Shun kitchen knives under their corporate umbrella. Kershaw brand knives are very good quality knives priced at a similar price point to Buck. Kershaw knives generally exhibit a more modern design look than Buck and they generally trend toward the "tactical" style of pocket knife. They make lots of flippers and for their price they are good quality with a good reputation. They even have some reasonably priced custom-maker collaboration knives.
Zero Tolerance knives are the high-end brother to Kershaw knives. With ZT knives you get designs that are very similar to Kershaw (flippers and more flippers, & lots of tactical looks) with better quality materials. ZT uses more titanium handles and high-end "super steels" for blades, with super slick ball bearing pivots. ZT is making knives with the same quality of materials as Benchmade or the high end Spyderco knives.
Benchmade is striving to make the knives today that you will want to pass on to your children or grandchildren in the future. This comes directly from what they told me during a private factory tour I had at Benchmade last week (Thank you for the tour Derrick!). I own over 2 dozen Benchmade's and I can say that I will indeed pass on many or all of them to my kids one day. They use high quality materials and maintain tight tolerances of less than .001". The designs are modern and very functional while also aesthetically appealing. They offer a wide range of styles and designs from tactical to utility. Their Axis lock is widely respected and many people have come to favor that locking mechanism. Benchmade is considered a high priced knife company because nothing they offer sells for much less than $100. That said, they make knives for people that want the high quality that you would pass on to future generations.
Spyderco, like Benchmade is making some of the best knives on the planet right now. Spyderco is different from the other high-end manufacturers however, in that they offer a full range of knives from the very low-priced to the very high priced and everything in between. Spyderco tolerances are kept to less than .0005" (half a thousandth) so you can count on first rate quality of construction regardless of the price-point you buy into. The biggest difference with Spyderco however, is function. When you look at a Spyderco blade and see the hole, and the bump (thumb ramp) over the hole, and a leaf-shaped blade you might think it looks odd. When you use a Spyderco design you realize there's a lot of beauty in function. These knives are incredibly well thought out designs that have better ergonomics than anything else out there (IMO). They are built to be great cutting tools and making them "pretty" is (although important, particularly to Eric Glesser) is second to making them function better than anything else.
I have a large knife collection that includes over 2 dozen of the best (highest-end) Benchmades, 6 ZTs, dozens of Spyderco knives, a couple of old Bucks and a few other brands as well. I have visited the Spyderco factory. I have visited the Benchmade factory. I have visited KAI USA. After using them all regularly and for a long time I tend to find my Spydercos in my pocket more than any other. Each person has different priorities. For me, I want the best quality knife that I would be willing to actually use regardless of price. Based on that criteria, my top 6 "best" knives are all Spydercos (5 made in Taichung, 1 made in Golden Colorado).
As far as customer service goes, I have not dealt with Buck so no opinion to share there....but I have dealt with ZT, Benchmade and Spyderco and all were very good experiences.