Not that there's anything wrong with them , its just that I got tired of having many little cheap boxes. I'm a neat freak and like to have everything super-organized so I recently splurged for a pair of
C&F large waterproof boxes. More for convenience than the waterproof feature. The two boxes fit perfectly in the two large front pockets of my Fishpond Gore vest. I like the pop-in replaceable inserts as well as the optional flip page that adds even more storage. These boxes hold a ridiculous number of flies, and if you think about it, the per-fly cost is probably better than some of the lesser expensive priced models.
One box is for my streamers, wets, egg patterns, caddis (dry, pupa, & larva). The other box is for mayfly dries, mayfly nymphs, midges, tricos. I have one extra insert that contains only terrestrials (hoppers, ants, etc) and easily pops in for late summer fishing when I need it.
Since I don't want to deal with putting used flies back into the micro-slits streamside, I use the two internal foam ripple patches that come with the Fishpond vest. When I get home, I hang the vest up, open the zippered pockets, the inserts flop down to a 90 degree angle, and I let the flies air dry over night. Fluff them up the next day and back in the fly boxes they go (using tiny pliers).
Two boxes, that's it. For me its peace of mind.
As far as SR flies go, I use my crush-proof Morrell boxes. IMO, they're very well suited for those conditions. Big flies (size 2-8), heavy gauge hooks, possibility of cracking or even losing an expensive box if you trip while chasing your fish, etc.