In terms of design, I'd agree with everyone else: there's no evidence of unreliability with the general design. As far as pure implementation details go, REKAT had some problems with the springs early on which caused reliability problems that have long since been fixed. They also had some problems where a shock to the knife could disengage the spring and render the lock useless -- this might have been related to the spring quality mentioned above. Also, in theory, since REKAT has only one spring, that's an obvious single point of failure.
I've not heard of any Benchmade spring quality issues, and there are two in any case, so the system is fail-safed. The stud on the benchmade sticks out farther, so in theory it's a weakness, though I've only heard one report of it being a problem.
All in all, any difference in reliability is probably nothing but statistical noise. If you're having trouble picking between knives from each company, pick whichever knife was built better, feels best in your hand, and meets your needs best. I don't consider lock reliability to be in favor of either company, both locks are great.
Joe