with diverio, manufacturers have to take the heat for garbage or go under, and the reviews in RSD do sometimes trash products.
My advice would be to take it all with a grain of salt and try out the one(s) you are interested in. Usually someone you know, or is known to someone you know will have one you can try. If not try a post on the board to find someone in your area. Also some of the bigger shows offer pool try outs, and some shops rentals may be the type you're looking for.
The other side is that there are some average performing standard regs that are always a reasonable value, and if you stay in the sport more than a season or two you'll get a back-up reg anyway, so buy it first. Plus, someone here may even point out a web site so you can save money and kill an LDS (but that is a different thread.
I have four regs, all working, one is a Royal Aqua-Master (older than most on the board I think), I have never regretted buying a reg, only ever regretted selling one...