As mentioned earlier, the difference is not a question of strength or thickness, but simply placement.
There is no difference in the lock performance of either in nearly all knives.
In many framelocks, the clip interferes with your ability to hold the lock closed with your hand.
In many liner locks, the liner is exposed and receives the same finger pressure that framelocks supposedly benefit from.
In either of these cases, adjustments in grip can actually unlock the knife, where a conventional liner lock would be immune.
Frame locks are generally thinner, due to design, while liner locks, in theory, have the potential for better grip.
Lockbar thickness, past a certain (and mild) point, has very little relationship to lock stability. A huge lockbar will not be more reliable, in the real world, than a medium sized one. This is because both will be far more tough and reliable than you will need, and further, cross-lock stability is based on many things, not only lockbar thickness.
The difference, in performance, of a good framelock and a good liner lock, is virtually entirely in people's heads. When liner locks were being made by ever cheap manufacturer out there, frame locks were starting to come out on some very high end models and still have a tendency to occupy the high end. The production quality made the huge difference back then. But now you can find Strider liner locks, etc. I personally find Benchmade liner locks to be brilliantly designed, having owned liner locks from all of the big three and many other companies.
But the JYDII lock is quite nice too.
Cross locks, as a genus, aren't particularly good not because of their integrity, but because other locks can be as strong or stronger while being easier to deploy and reclaim. The axis, BBL and of course, the hawk lock, come to mind. Not to mention that weird breed that is the compression lock--much stronger, much more reliable and much easier to use than its predecessors.
