I bought their other model, the one with a front zip opening and two small, concealed slit pockets. It has a large compartment in the back to hold a water bag similar to Camelbak.
I love this flotation aid (they do not call them PFDs) for one overriding reason: it FITS ME! The sizing comes in finer increments than the typical US-labeled XS/S, M, L, or some overly wide variation thereof, which have no size between Kiddie and the smallest Adult. None. A lot of people fall into that size range and have to tolerate gigantic, obstructive PFDs. OR they say screw it and just carry the PFD on deck without wearing it. I’d rather wear a proper fitting one then do that, but if I can only have one that doesn’t fit…
It also is neither too short nor too long, and it is not too thick. Yes, the flotation for my size is less than that of the usual one-flotation-standard-fits-everybody level of about 16 lbs. But I do not need 16 lbs to float me! The foam is obstructively bulky. A large youth-size PFD (9 lbs or 11 lbs, depending which PFD brand) floated me just fine, which I did test.
My Vaikobi had no trouble floating me in fair-sized waves, so it’s not just a calm-water thing.
Caveats: I absolutely will not endorse it for SINK paddling, even though I would use it for such myself. The manufacturer designed it with surf ski aficionadoes in mind, and those paddlers can swim and tread water. It is obvious that US PFDs are designed for the lowest common denominator, “everybody.”
You don’t say why you are considering a Vaikobi or one of the other foreign-brand flotation aids. If it is not about sizing or high torso mobility, there may be no advantage.
As for heat buildup, it’s not a mesh-heavy design. Surf skis and SOTs in general are not heat traps, since there is neither a top deck or a sprayskirt, and they are a wet ride despite bailers, Venturis, or scuppers. A PFD designed for hot climates, such as those with mesh backs, might better suit summer use in a SINK.