...both your choices are decent regs, I'd focus on whether or not your favorite local dive shop services/supports your given choice. For what it's worth, I own/dive a variety of regs (Poseidon Jetstream / Atomic B1/T2 / Mares Ruby / Mares MR16 Voltrex / Apeks XTX 200 / Aqualung Titan LX), I've never dove a Zeagle, but overall the public seems satisfied with them...as far as the Mares, while I've never dove the Proton, I've taken my Mares down to 150 ft. deep and been very happy with both models, very reliable with fine performance.
These days I mainly use my Jetstreams for diving doubles.......my Titan LX is my 'loaner' reg...and I mainly use my Atomics and Mares Ruby for single tank diving.....my Apeks XTX 200 is due to arrive next Wed, when I test it out for a week in the Turks and Caicos Islands the end of this month I'll decide how it compares to the B1 and the Ruby.....will be interesting!
Karl