My thought is this: If you think you MIGHT ever want DIN regs, then get DIN. You can use a DIN reg with a Yoke adapter. But, you cannot use a Yoke reg on a DIN-only tank, period. . . .
I disagree. If the OP "MIGHT ever want DIN regs" but does not really need them for the foreseeable future, then I would recommend the OP get yoke regs. As far as I am aware, the ONLY region of the world where dive ops might only offer "DIN-only" tanks is Europe. Few Americans go to Europe to dive. My impression is that pretty much everywhere else in the world, including all the popular tropical destinations, dive ops' rental inventory will consist largely or even exclusively of yoke tanks or convertible tanks.
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I suspect everyone would agree with that.If you are only going to travel to tropical destinations and rent tanks, then you should be just fine with a yoke reg.
The only downside to DIN is that it MIGHT cost you a 1/4" of clearance behind your head if you have to use a yoke tank. For me, that would not matter and, honestly, I'm unclear on how it affects other people. . . .
I think it's a little more than 1/4 inch, but regardless--it does annoy some people. Maybe we're the minority. But the OP should be aware. The silver lining here is that is someone buys a DIN reg and later decides that the adapter annoys them, the DIN fitting on many regs can be replaced with a yoke fitting. I have even heard of some people doing this conversion on an ongoing basis instead of using the aforementioned screw-on adapter. It takes a couple of tools, such as a crescent wrench and an Allen wrench, and some might advocate a torque wrench for installing the yoke fitting, but it's still just a few minutes work.
I would agree there USUALLY is "no trouble getting DIN tanks." But except for Europe and places that cater to technical divers, the majority of most dive ops' inventories will be yoke, not DIN. You often have to ask for DIN specifically, or they will assume you want a yoke tank. If you forget to ask in advance, they might not have one for you at the last minute. Even in S. Florida, I ran across this. "Yeah, we have DIN tanks, but they're all rented out at the moment--we should get some back tomorrow."
Me--as I said, I'm happy with yoke on my recreational, single-tank reg set. If and when I buy a set of doubles, I'm sure I'll buy a separate set of DIN regs.