As always, one of the key questions is "Where can I get my brand of reg
reliably serviced?" If you haven't got local service for that brand, that really limits your choice. If you do...
The 62x is most correctly compared to the Mk11, since both do not have environmental sealing.
The 62x TBP is comparable to the Mk17, as both are sealed regs.
The Mk19EVO is sealed AND has a rotating turret.
So if good service for both brands is easily available to you, the real question is, "Do I want a rotating turret?"
- The reg is much heavier - most folks don't care.
- The reg, when mounted turret up can bang your head. When mounted down, the advantage of the turret is limited, though the fifth port is nice if you want a longer hose to route down under your arm.
If you don't need a turret, sealing for a diaphragm is pretty meaningless. You just rinse out the spring hole after a dive. It
might help a little if you dive really cold water.
The second stages are comparable, both with excellent performance. But one question is why do
I definitely need an "adjustable breathing resistance knob."
?
It's an occasionally helpful adjustment for my
auxiliary reg for giant stride, to decrease freeflow chances. But then, I have to remember to turn it back once I'm in the water, so I don't hand my panicked OOA buddy a stiff reg.
For my primary, if properly tuned, I literally NEVER touch the knob.
Frankly, the biggest reason for an adjustable is that nowadays, if you don't have regs with knobs, some divers will think that you can't afford better gear. There is
almost no reason to ever stiffen your breathing by turning in the knob. Maybe at the end of the service interval, if your reg is dribbling a little air and the valve doesn't quite seal, you can finish a dive trip with the knob turned in 1/4 turn. That's about it.
Both the reg sets you mentioned are excellent. But the firsts are a little different from each other in features. As mentioned by others, this forum has LOTS of Scubapro fans. Scubapro makes excellent gear. But so does Mares and it's really all just personal preference.
IF you can get good Mares service where you live, at this stage in your diving career I'd save the extra money and put it towards another toy.