I started with a Balance and now have a BP&W with ACB. I think that weight integration simplifies the donning/doffing. IMHO anything that is not attached to the BC increases the task loading, one more thing to remember. I also feel that weight integration pouches are a lot less likely to shift position and/or fall off. While Ive heard stories of integrated pouches inadvertently falling out, Ive never seen it. I did find a lost weight belt on the bottom of Millbrook and latter found the owner who said it fell off during a night dive.
On all the boat dives I have been on but one, I climbed out of the water with all my gear (except fins on certain ladders) so the combined weight was not an issue. One time I was low on air and handed by BC to the DM so I could snorkel around on the surface, looking at the Eagle Rays. I handed him the ACB pouches first, which have handles making them easier to handle than a weight belt.
The big advantage to a weight belt is the flexibility of moving weights around on the belt to adjust trim, but I think this is less of an issue as you start diving with steel tanks and back plate and reduce the amount of weight youre caring. I suspect it is also harder to replace certain integrated weight pouches, since Ive never seen them for sale. Thats a bad thing if it results in reluctance to drop them in an appropriate situation.
This is one of those questions that doesnt have a right answer, it comes down to personal preference. But it is also one of those issues for which divers will come up with antidotal stories to defend their position to the death. A funny exception is DIR divers that believe in weight belts but are prevented from lambasting weight integration because Halcyon makes the ACB system; but I digress.
If you do decide to go with weight integration, keep in mind that all are not created equal! There are some that use a complex cable routing mechanism to hold the weights and some that use pouches. I prefer the pouch systems and personally would not use a cable system unless the only other option was to not go diving. The pouches are easier to load and unload and can easily be handed to someone. If you drop them youre looking for a pouch not individual weights on the bottom.
Again Ive heard stories about the Velcro failing and the pouches falling out. I cannot imagine this happening on my Seaquest Balance. Even if the Velcro were not fastened they would not fall out because of the curved shape of the pouch and receptacle. Maybe in the early days of implementing weight integration there were problems. And perhaps some cheap BCs manufactured have problems but as Ive said, I havent seen them
Mike