Hands getting cold is a difference, at lower temps you better have dry gloves. Free flow is BS, there are bulletproof regs that will ever freeflow (unless the suffer a first stage seat problem or other mechanical failure) as long as proper procedures are followed. ScubaPro just doesn't happen to head that list....
... I have never seen a Cyclon 300, a Sherwood Magnum Blizard, or an AGA, freeflow from cold. Hell ... I used to dive Oceanic Omega and Omega IIs up there and I'd come out of the water with an iceball the size of a grapefruit around the first stage ... but no freeflow.
Your statement is not quite fair nor entirely accurate. The MK 25 is indeed a poor choice for cold water but people seem to make the mistake of associating that with all SP regs. That is not the case. (Of course it does not help that SP pushes the POS Mk 25 as its premier first stage.)
- The MK 5, MK 10 and Mk 15 first stages with SPEC kits were basically bullet proof in cold water as long as the silicone in the SPEC kit was topped off mid season. I got the same level of reliability with the Mk 20 using MK 15 SPEC boots and dove them for years. A few times at the end of an ice dive I tried to provoke a freeflow with an extended full blown purge, but could never get the first stage to freeze flow.
- Poseiden or other first stages using alcohol or silicone oil have the same limitation as a SPEC sealed SP reg in that they are only effective if they are well maintained. In my experience both alcohol and silicone oil filled ambient chambers are prone to leaks over wide temperature extremes.
- The sherwood air bleed system works very well as long as you do not make a rapid descent that exceeds tha ability of the sytem to maintain a dry ambient chamber.
- The current Mk 17 is also extremely relaible in cold water and is dry sealed requiring no mid year maintainence. It also survived high flow rates at 165 ft for 200 minutes in 35 degree water - the only first stage of any manufacture to do so.
- All single hose second stages are prone to freeze flows in near freezing water if the flow rates are high enough and the internal parts get wet. More metal will improve heat transfer and is always a plus in cold water. The same thing applies to an Aga with the chief advantage being that the reg tends to stay drier inside. Of course if you get a freeze flow, life gets interesting if you have to change shut down a post and switch to a backup mask underwater.
- Double hose regs have by design both first and second stages that are dry sealed and in addition the large cans provide superb heat exchange. Consequently, they are, depsite the age of the general design, the most bullet proof cold water regs you can find.
With regard to dry gloves, they are not required even on extended ice dives. The critical issue is the core temp. If your core temp starts to fall due to inadequate insulation, your body restricts bloodflow to the extremities and dry gloves or not your hands will get cold. Conversely if you keep your core warm, your hands stay warm even in wet gloves. I routinely use good quality 5mm neoprene gloves on ice dives. Use newer gloves that are not yet leaking badly in the seams and use gloves that fit you properly along with adequate dry suit insulation and your hands will do fine.
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