If we're talking about folders as the original question referred to, to me the biggest issue is lock strength. The linerlocks are starting to show serious problems across the board where "combat applicability" is concerned...if you spend $250+ on a REKAT with the Rolling Lock and it will NOT collapse no matter how hard the spine is hit or how much you twist, wrench and grab at it, is that worth it?
That said, the relatively "cheap" Cold Steel zytel lockbacks have VERY strong locks. They're not exactly smooth, and I'm getting a certain rep for the "dremel modification recipe" I came up with to smooth out the snapopen sequence. EMail for details
. I *like* my Cold Steel Vaquero Grande and when I can't wear a fixed blade it's an excellent defense knife. It can be improved on, and I'd spend more on a higher quality "megafolder".
(Note: Calif. has no blade length limits on concealed megafolders. I keep threatening to jigger together a folding Katana using a hacked Ontario Black Wind 1095 20" blade...