My Seaqeust ProQD+SL has pretty resistant-to-drop weight pockets. I've had more issues with belts than with the pockets (something to do with my shape). My evolution was:
1. Weight Belt
2. Integrated Weights (bought own BCD - ended up with 5kg(11lbs)+steel tank with 7mm+7mm vest in the end)
3. Integrated Weights + Belt (bought dry suit, needed extra weight, started with 14kg(30lbs)
4. Integrated weights (bought lead slabs more suited to the BCD pockets, currently with 11kg(25-26lbs))
Next evolution is going to be BP/W+Doubles. I'm going to go with integrated non-ditchable - V/P weights - and any remainders on a belt, if necessary. Having some ditchable weight is not a bad idea, if I ever dive wet with the doubles rig, I suppose.
My experiences:
Belts hurt your back if you have loads of weight on them.
+SL pockets work reliably, providing you click them shut correctly. The velcro-only pockets are the ones that drop.
it is easier putting in pockets in the water than belts, even with thick gloves (part of CMAS** is removing and replacing your weights underwater)
Never had an issue in needing to separate myself from the rig. Going to be even less so with the doubles when I can reach my own valves.
Weights in the BCD help rotational trim, as they keep the C.o.G. below the C.o.B.
With a dry suit, the amount of weight I would have to belt on would make the belt excessively cumbersome. Any more than 12lbs on a belt gets awkward in my experience.
Gerbs