Objectively, Poseidons regulators are some of the most capable regulators on the market for cold water diving. I don't know any other that fulfill Norsok U-101 for example. Then again, some people hate the way Poseidons breath, while others love it.
Mares Abyss 22 is extensively used by the navy and passed their cold water tests.
I don't know what type of diving you have in mind and how extreme your dives will be. Is the water temperature not colder than 4°C and the depth not more than 50 meters? Then any regulator that fulfills EN250 will do.