If you plan to dive in water less than about 50 deg F, you need to consider diaphragm type first stages (so sayeth the Oceanic Owners Manual; none of their piston regs are suitable for use below 50 deg F). If you are looking at a reg with a piston type first stage, read the owner's manual to see if it can handle cold water. There may be an environmental kit but, at least, Oceanic says no.
AquaLung, on their web site, has a snowflake icon along with descriptions of regulators it considers suitable for cold water. I think one of these is a piston reg so it probably has some kind of environmental kit. But, at least AquaLung comes right out and says which regs it would recommend.
NOAA, the US Coast Guard and the US Navy have selected the Oceanic Delta4/FDX10 as their cold water regulator of choice. I would imagine the EOS is an improved version but I bought the Delta4 for my wife.
The ScubaPro Mk17/G250V is highly regarded as a cold water regulator.
I guess I would stay with the top 3 players: ScubaPro, AquaLung and Oceanic. I KNOW there are other players that make very fine regs but the big 3 are probably easier to get serviced around the world.
If you can get by without the DVT (drive valve technology) and swivel at the second stage, here is a pretty decent price on the Delta4:
Oceanic Delta 4 Non-Swivel FDX10 Non-DVT Regulator
Here's the same reg WITH DVT for a better price:
Oceanic Delta 4 DVT Regulator
I never thought I wanted DVT because I don't want another gadget in the airstream. But the way the other folks around here forget to tighten the cap before rinsing is beginning to change my mind.
DIN vs yoke: good luck with that one! I guess you are better off to have a DIN reg and Thermo PRO valves on your own tanks but you will need a yoke adapter for rental tanks.
Good Luck
Richard