I use those Ist dumpable weight pockets on both my doubles and single backplates. A big advantage is if you lose the inner pocket for any reason, you can use almost anything in an emergency. If you lose a special pocket, you may not be able to find a local replacement. The buckles on the Ist are very secure as they will only release when both the top and bottom parts of the mechanism are depressed. I have had other recreational bcd pouches release by getting caught on other divers gear in a boat. Similarly, we have had students lose recreational bcd pouches by having them caught on lines, railings, etc. This simply cannot happen with the Ist pockets.
The more expensive xdeep pouches of the same basic design have better features such as a hold open edge and are more robust.
The eyelet in the webbing is important in preventing the entire pouch from shifting. As previously mentioned some plates do not have a hole in the correct location. It is easy enough to drill one yourself. You can also use a wire tie to secure the eyelet if you don't want to or can't drill the hole.
We use the two piece tank bands because they are easier to put on tanks. For trim weights on the tank band, the best is the dive rite travel buckle triglide model. This dive rite model is the only pocket that has a triglide so that the position of the pouch cannot move on the band even if there is weight in the pouch and the band is hanging loose in two halves not on a tank. The webbing loop on other manufacturers models are looser and may slip. It is rated for only 4 pounds, but I routinely use 5 pounds and you can actually squeeze a 6 pounder in there. The buckle on the flap also positively precludes accidental loss of the weight. We have seen weights lost out of Velcro only trim pouch flaps.
We use either plastic or skeletanized stainless plates to minimize travel weight. An additional advantage of this is that you have more control of your trim by using weights versus the use of a solid plate or a steel tank.
