In my opinion, the 2 best values in regs on the market today are the Atomic Z2 and the Deep6 Gear Signature series. They are both as good as any reg on the market, at any price. But, they are both very inexpensive (as quality reg prices go, anyway).
If you want something that you can have serviced most anywhere (location-wise, not necessarily most any individual shop) and expect them to have parts in stock, go Atomic.
If you are going to do self-service or are comfortable mailing your regs off, then Deep6. Lots of shops will not service any brand they don't sell. It's an issue of liability. So, getting Deep6 regs serviced in any particular area is likely to be more difficult than getting a ScubaPro or Atomic reg serviced.
For single tank diving, there is nothing up the Atomic chain that is "better". Only regs that have features you don't need for single tank (like a swivel turret) or more expensive materials (like stainless steel or titanium). As someone already said, the Z3 just gets you a really expensive proprietary swivel hose. You're much better off to buy a Z2 and a Cave Adventurers swivel (for $25) if you want a swivel.
I currently own ScubaPro Mk 25 EVO/G260 sets, Atomic M1 sets, and an Atomic Z2 set (and a Hollis DC3/212 set and Dive Rite XT1/2 sets). The Z2 and Hollis sets are for single tank and all the others are for doubles or bailout/deco.
In ScubaPro, I like the Mk 25 EVO/G260 combo better than any other ScubaPro option. Bonus that it less expensive than several of their other options. But, I like the Atomic regs better. They all breathe the same (to me). But, the Atomics are (or can be) sealed. And the 2nd stages (from Atomic) all have the AFC, instead of a Dive/Pre-dive switch to futz with, and they have the Seat Saver setup, which, in theory, will let you tune them for the easiest cracking pressure without having them start to leak just a tiny bit after a while because the seat in the 2nd stage eventually gets worn a bit. Or, I should say, they'll go a lot longer before that happens. I suspect this does not happen to a lot of people, ever, simply because their 2nd stage is not tuned for as light a cracking pressure as it could be. Probably because the tech didn't want it to come back in a month or two because it's starting to leak just a little bit...
I think the Atomic Z2 is nicer than any ScubaPro that is anywhere near comparable in price. And the Atomic M1 is a bit nicer than the Mk 25EVO/G260 - and it's less expensive, to boot.
I do not find any use for a swivel turret on a single tank reg set. But, I do like having a bottom port (which the Z2 does have). That lets my octo hose come out of the bottom port and route under my right arm without sticking out to the side (from the 1st stage) and then bending down to go under my arm. It's a small detail, but I like it that way. It is just that much more streamlined. Also, if you have a Z2 and you ever decide you need it to have a swivel turret, your Atomic dealer CAN get the parts and convert the Z2 to have a swivel turret.
Regarding any thoughts of servicing your own regs, there are many things to consider. My path has been this: I worked for a shop for a while. I went to ScubaPro Reg Tech school and got trained up to what they call Level 2 ("Pro" I think they call it - level 2 of 3 max). My plan was to start servicing my own regs. I had not switched to Atomic at that point. SP were my main regs.
Then I looked into all the equipment I would need to buy to do it properly. Various tools plus things like an ultrasonic cleaner. It was not going to be super expensive. But, not cheap, either. Then I thought about how often I would actually use all that equipment. Good regs do not need to be serviced every year. Once you know how to do basic tests on them to assess their status, good regs probably don't even need to be serviced every 2 years. Or even 3.
So, I was looking at shelling out a chunk for tools and then only using it maybe every 2 years (or more). At that point, I started thinking about whether I would really want to trust my regs to be serviced by someone that only does a few regs, once every 2 or 3 years. Even though it was myself. Yep. Nope. That is when I decided to save that money I was going to spend on tools and be happy that I understand how they work and I can do basic stuff myself - and diagnose them myself to know when they really need to be serviced. And when they do, I will have somebody service them who does it all the time and that I trust to do it right. YMMV