MichaelMc
Working toward Cenotes
I'd skip the Conshelf 1085 and SP 108, and any other unbalanced ones that do not have a later balanced form. I got a 108, but it didn't tell me much about the later barrel poppet based regs. And non-adjustable means trading off free flow vs ease of breathing. I like adjustable.
The SP 109 is really easy. I got two and upgraded one to balanced, my shop actually then put SP HP internals in it. I use it as my secondary. The unbalanced 109 and a Mk2 are in my save a dive kit.
My Deep6 primary is very easy and similar to other modern balanced second stages. It's just mildly more complex that the balanced 109 due to sealing the venturi dive/pre-dive vane and the metal barrel in a plastic case.
The old metal cases are nice to work on as they avoid the barrel-case and venturi o-rings. Just less clutter to comprehend when starting out. If you can mentally set that complexity aside, there is no reason not to go with a G250/260 or the Deep6. Or Apex, etc. The G50/260 should keep lower work of breathing than the 109/156s at high exertion, but at normal even hard swimming I am equally happy with my 156 and Deep6.
Some of the old G250 line have more complex balancing internals, I'm not an expert on that. I haven't ventured into my S600 seconds.
I started tearing apart and servicing some of my regs about a year ago, so this is just my experience. Again, the 109 and balanced 109 are really simple and parts are available and cheap.
The SP 109 is really easy. I got two and upgraded one to balanced, my shop actually then put SP HP internals in it. I use it as my secondary. The unbalanced 109 and a Mk2 are in my save a dive kit.
My Deep6 primary is very easy and similar to other modern balanced second stages. It's just mildly more complex that the balanced 109 due to sealing the venturi dive/pre-dive vane and the metal barrel in a plastic case.
The old metal cases are nice to work on as they avoid the barrel-case and venturi o-rings. Just less clutter to comprehend when starting out. If you can mentally set that complexity aside, there is no reason not to go with a G250/260 or the Deep6. Or Apex, etc. The G50/260 should keep lower work of breathing than the 109/156s at high exertion, but at normal even hard swimming I am equally happy with my 156 and Deep6.
Some of the old G250 line have more complex balancing internals, I'm not an expert on that. I haven't ventured into my S600 seconds.
I started tearing apart and servicing some of my regs about a year ago, so this is just my experience. Again, the 109 and balanced 109 are really simple and parts are available and cheap.