On your backup regulator you probably don't need it, especially if you are doing mostly recreational dives. You get the most use out of it on deep dives where the air is denser.
Originally posted by zygut
So the difference is in number of ports and if it swivels or not, and the DST has a 1/2 MP (medium pressure?) port. It sounds, from the rest of your post, that the swivel is *not* a good thing? Why is that? Remember you are talking to a newbie here
Correct, the DST has an enlarged primary port, that in theory provides increased air flow, but most people would consider the 1/2 to be non-standard (with 3/8 being standard). There really isn't a big advantage or disadvantage to it. It's just something to be aware of if you ever need to replace the hose.
As for the swivel, I personally do not like it, and I think you'll find that is the general consensus. Some people do like it though. I personally like having the orientation of my hoses fixed and not moving around on me during a dive.
If you get a DIN regulator, then you either need a DIN valve on your tank, or a DIN-to-Yoke adapter. If you are buying a tank, a DIN valve will cost about $20 extra and a DIN-to-Yoke adapter will cost about the same. DIN is actually a more secure connection than Yoke, which is why I prefer it given the choice (I would argue we are behind here in the US by having Yoke as the standard).
