Recently, Mares, the maker of the "Abyss", bought DACOR INC. As far as I know, the DACOR line will continue as separate branding and technology. These two companies have been making regs since the 50's and have it down cold. However, I think the Mares MR 12 type regulators(with the bypass tube)are more highly regarded than the "Abyss". The DACOR "America" and DACOR "metal" are side breathers and Rodales response was tepid. Actually, they tested the older "Vyper" and reported some wet breathing in certain positions. My understanding is that the later models I mentioned correct this. Neither of these regulator lines is second stage adjustable in water. However, this feature is personal preference more than anything.
Don't let anyone tell you that these regs or the Aqualung line, etc won't perform below 100 feet. All these midrange regs will deliver as much air as the Scubapro or Apex. Differences between these regs, to the extent reported, can only be detected by sensitive machinery; the diver won't see any difference. From the divers viewpoint, he will notice "ergonomic" differences such as weight, "pull" at the mouthpiece, bite, flexibility and position and length of hose, side breather or etc, bubbles, clearing. This is all the result of diver experience and prejudice and it is unlikely that someone can give other than general advice since your experience will almost always turn out to be somewhat different from another. Tests such as Rodales can give you a starting point.
Something to think about: Jacque Cousteau's team preferred the single stage, two hose "Mistral" in dives below 100 feet. This regulator was designed in 1955 and had six moving parts, half that of some modern regs. Yet, this ancient device provided adequate air for almost any situation. Regulators have come a long way in the last 50 years. The average diver would certainly notice differences between the Mistral and the G250 or whatever, but differences between equally modern regulators, as reported by some divers, are mostly nitpicking and/or speculation.