bit difficult to answer. Why do you need a FFM, and why did you narrow it down to those two?
My personal FFM is a Poseidon Atmosphere. I chose that because it is easily compatible with the rest of my regulators that are all Poseidon and I think it is more comfortable than the other masks that I've used. That said, it is not compatible with any sort of ambient breathing valve. I don't really think they're that necessary, but that's me personally.
I have a lot of experience with the OTS AGA and Guardian masks with preference to the Guardian for comfort and ease of use. The stealth is supposedly really nice with their new second stage but I haven't tried it yet.
@anelson-OTS can weigh in on whether the Spectrum ABV is out yet. I thought I had heard the MTS-ABV for the Mantis was compatible from someone, but could be wrong.
I know
@The Chairman has a Spectrum and he seems to be really happy with it. Big advantage to that unit is the silicone oronasal pocket that allows you to equalize normally *I don't have an issue with the blocks, but a lot of people do*, and it allows you to use your own second stages which is really nice. Not sure if you have any OTS, Ocean Reef, Poseidon etc. repair centers down where you are, but if you go with the Spectrum you won't have to worry about any of that while still gaining the ability to use a comm system if you want.
I personally put Ocean Reef 3rd on my list of FFM's for a myriad of reasons.
@Lake Hickory Scuba uses Ocean Reef's though and Bryan may be willing to weigh in on why he chose that. Video on the FFM in question below and there are several other FFM videos on the Ocean Reef line.
Regarding quick connects. With the Spectrum, since you are using your own regulator, any quick connects that you want to use are going to be available.
Link below to a QD from Omniswivel via
@Dive Right In Scuba who sells both masks in question. This will work on any second stage that uses a normal hose. The AGA and Poseidon require adapters that are also available from Omniswivel and DRIS has them on their website. IIRC the Neptune uses normal regulator hoses, the current Poseidon comes with a hose adapter to normal hoses as stock from Poseidon, and the Stealth masks from OTS use standard scuba hoses which is nice. With that, the QD below is great and will allow you to make any gas switches that you need however if you are planning on doing it regularly, I'd really recommend getting a switch block with a QD on one of the inlets so you aren't ever truly without gas...
Omni Swivel Regulator Quick Disconnect | Dive Right In Scuba - Plainfield, IL - Dive Right in Scuba