When I was certified along with my wife and two daughters, I bought 4 sets of cheaper entry level regs. As I accumulated dives and continued to feed my gear addiction, I found a great deal on a MK25evo/S600 from a dive shop with less than 50 dives on it, serviced and to my door for about what I paid for the cheaper reg. My wife tried it....and I had to get her one too. Same shop sold me an indentical set with less than a dozen dives on it for not much more.
Someone said, buy once, cry once. The entry level regs are fine, breathe easy enough, and have been bullet proof. They make great loaner regs and I use them as backups in classes. That being said, there is a difference. The high end regs breathe much better and drier in all positions.
I don't regret buying the entry level regs...I just wish I would have upgraded sooner.
I did buy a wing with the exhaust valve mounted in the center, I prefer my other wing with the exhaust elbow on the left shoulder. Again, not really a regret, but more of a preference.
Jay