I like folders and use them more on a daily basis than my fixed blade, but when outdoors, my folders are really limited to a quick cut of cord, possibly sharpening a stake or quickly trimming very small branches; the heavy duty chores are done by my fixed blade.
With that said, there are a lot of good blade locking mechanisms out there from the traditional lockback to the Axis styled locks. I've been very satisfied with liner locks form Benchmade, TOPS, Spyderco and Emerson; I don't trust most, but from reputable manufacturers and makers, they are pretty fool proof for normal usage. From an engineering perspective, Spyderco's compress lock (reversed liner?) is very secure and I really like them on the Spyderco Para Military models...one of my common EDC folders.
Spyderco lockbacks are pretty darn tough, but as mentioned, battoning a folding knife can damage most locking mechanisms over time...if done, it should be done rarely and within reason. Cold Steels mammoth Rajah 1 has probably the beefiest lock of any folder I've seen and the original Al Mar SERE has a very robust lockback as well.
Framelocks are pretty stout if well done as well. I'm pretty comfortable with my Sebenza's locking mechanism.
The Axis styled locks have been out for some time and I haven't heard much other than if they aren't maintained, they can get gunked up.
I do have a couple of Benchmade Balisongs and they are good locking mechanisms...for the most part, very similar to the Paradox from Cold Steel. As with all folders, it's not always the locking mechanism that is the issue but the inherent issue that the blades "tang" is always going to be short and you're relying on beefy, well constructed scales in conjunction with the locking mechanism to provide the necessary strength for tough uses. Lateral stresses are the worst and what should be avoided the most.
I would have to say the dual locking mechanism of the Extreme Ratio RAO folder is most likely the toughest folder I own. It's still not a fixed blade and it could be used roughly, but if I can, I'll rely on a fixed blade for the more abusive knife chores. If you're limited to a folder, just understand there are limitations and limit the abuse that affects their weakest aspects (lateral stress and hammering against the strength of the locking mechanism.
ROCK6