hey Pesh,
I've owned both and the only one I've had fail was a linerlock... twice: a liner lock can fail if the knife gets twisted in your grip, thus pushing the locking bar out of the engaged position.. which happened to me. The liner lock can also fail if it's not properly engaging the blade... which happened to me, but it was a new knife and the maker remedied the problem before it ever became a problem.
I've never had a lock back fail, but I've never abused one to the point of failure.. and I really hadn't abused the liner lock, either, it was just a little too exposed and would unlock when twisted in my hand.
Personally, I think they are both good basic locking systems, and if done properly, won't fail until you've really gone beyond the limits of normal use.
Course, the point in having a knife is for those moments when you may exceed "normal" use... like cutting your way out of an inverted semi, cutting your arm off to save your life or prying a jammed minigun loose while being shot at... All situations where a folder would probably fail.
I've watched Lynn's ads for some time, and I own a few of the early Cold Steel tantos... I just never really liked the style of his folders, but I do think his knives are extremely ruggedly built. Personally, I've used liner locks, back locks, Axis locks and several other kinds of locking folders... Under normal use, you'd be hard pressed to find one that failed under any but the most extreme circumstances.
You can also do a search here on that very question, as you're not the first to ask it, nor will you be the last!
BTW: welcome to the forums from another Washingtonian!