I actually own all three regs that you are considering - Mk 25/G250, Zeagles (I have a couple of flatheads, 50Ds and DSVs) and the SR-1. Sherwood supposedly has the hp issue fixed and if that is true, of the regs you mentioned, it would be my first choice. It is environmentally sealed so cold and/or contaminated water are not issues, breathes great and has a small second stage which really does reduce jaw fatigue. My second choice of the regs you listed would be the MK25/G250V. I prefer it over all of the Zeagle regs for a couple of reasons - mostly related to the first stage: it has better hose routing options, particularly for doubles, but even for a single tank setup, I think it routes cleaner, breathes better (in my opinion) and you are more likely to find ScubaPro support on an international dive trip than Zeagle. I would not consider a SP diaphram reg (MK17). If you want a diaphram regs, then get the Zeagle.
If I had to go out an buy one tomorrow and leave immediately on a dive trip, I'd get the SP just because it is tried and true and you can be sure that it will work. I do think the benefits of the Sherwood are worth the possible hassle of the hp issue if you can put a couple of dives on it before taking it on a trip.
Jackie