CJFor - 7/25/2017 9:39 AM
DamnYankee,
I am in a similar boat, I just finished my AOW and have been renting gear all along, and feel it is time to take the plunge into my own set of gear. I have been doing a lot of research, and I just started working in a dive shop part time, so I have been soaking up information like a sponge.
DIN vs. Yoke. Yoke by far is the most common, but there are places that have DIN rental tanks. If it is a concern you could alway buy a DIN first stage and put a yoke adapter on it, giving you the best of both worlds.
Balanced vs. Unbalanced. It really comes down to two things... Price and personal preference. A balanced first stage will give you the same "work of breathing regardless of tank pressure, meaning that it will breath just as easy with 1000psi in the tank as it will at 3000psi. An unbalanced regulator will make you work a little bit harder get a breath of air as the tank pressure drops, because there is not as much force compressing the springs within the first stage. Like I said, personal preference is a huge part of it, you will also pay a bit more for a balanced first stage.
Diaphragm vs. Piston. Piston is your most common regulator, and they are more susceptible to freezing when diving frigid waters. A piston reg is just that, a piston within a chamber, as high pressure air is squeezed through it creates condensation which can potentially freeze causing a lack of air or a free-flow situation. As Eric_R said, just make sure the regs are rated for cold temps. If you will be doing a fair amount of ice diving you may want to consider a diaphragm reg.
Hopefully I answered your questions! Honestly, your best bet would be talking to a few local shops. Preference and budget has a lot to do with buying equipment. quite a few shops will take used equipment on trade, so you may be able to trade in your old stuff and strike a deal, or maybe they have some used equipment that may suit your needs and budget.
Sorry for the novel! Best of luck in your search, and stay safe!