For me, the point is service. I know I probably won't have trouble getting my ScubaPro regs serviced, pretty much wherever I go. As I travel a lot and move pretty frequently (e.g. from Oregon to Guam--where there is also a ScubaPro dealer--in a month), that's a major issue for me.
Because I am not servicing my own stuff, it's pretty important to me to be able to have somewhere local to get work done. I'm not completely opposed to shipping stuff off for service, but the added cost/hassle and potential for long-term inconvenience ("What? Oh, we don't service/sell parts for that brand any more; it was just a private label.") just isn't worth it to me.
As for safety/quality/actual parts, I have no experience in the scuba industry, so can't comment. Private label OEM manufacture is exceedingly common, especially with the computer industry, and the results can be a mixed bag. All of Dell, HP, Apple and Acer's laptops
are made by OEMs in Asia (primarily Quanta and Compal). These folks also make laptops for smaller companies/labels (e.g.
ADK uses Quanta,
Averatec uses Compal), which may be of comparable or better quality, but getting replacement parts if your private label goes belly-up may be impossible. Not that getting parts from a big name is always easy, but my experience is that the odds are better.