The bottom line is that virtually any regulator you buy is going to work -- no company can afford the liability of selling unreliable equipment. ScubaPro equipment tends to be expensive, but on the other hand, the company supports the gear it makes for a long time, if not forever, so if you keep your regulators, it's unlikely you'll ever find yourself unable to get them serviced. The company also has good worldwide penetration, so again, anywhere you end up living, you can probably get your regulators repaired.
In general, the "newest" and "fanciest" stuff is the most expensive, and most of the bells and whistles that make it so (titanium regulators, multiple user adjustments) aren't very useful.
There ARE some characteristics of regulators that make them preferable for given applications. Environmentally sealed and diaphragm regulators are preferred for very cold water use (although my MK25/S600 piston regs have served me quite well down to 41 degrees). Regulators which take standard hoses are more convenient (but, to my knowledge, the only ones nowadays that don't are Poseidons).
In short, buying a middle-of-the-road regulator from a widely distributed company is probably a very good strategy.
As far as BCs go, the very biggest thing is fit. A BC doesn't just have to be comfortable -- it has to hold the tank solidly and stably in the middle of your back. What feels good to walk around the shop in may actually have very poor function underwater. That's one of the reasons it's good to borrow or rent a few times before plunking down the money to own something.
