before announcing my decision and my purchase. 
Though every unit has something that I like over others, in the end, I decided to go with the Dive Rite O2ptima for my purchase. Here are my reasons. They might not be right for you, but they seem to make the best sense for me. You're not going to rain on my parade, are you?
There were several things that I like about the design. I actually like the Extend Air cartridges. I think that they will give a consistent performance when compared to potential variations in scubber pellets, settling and packing issues. I also like the idea that they produce no dust and can easily be changed on a boat.
I am okay with paying extra while the cost to fabricate the cartridges comes down. I am pretty confident that the duration testing will give me sufficient bottom time when newer tests are published. If I am limited to only three hours or so on a dive, I can live with that compared to the 20 minutes I am averaging on my deeper dives now using open circuit.
I really like the horizontal canister mounting. The hoses route really well from this, and I think that they present less of an entanglement hazard in wreck diving. I also think that this contributes to the overall low Work of Breathing.
I actually like the cover (though you might not). Rather than being the hard plastic which can look pretty bad after a few dives, the O2ptima cover is thin, soft and durable. After spending this kind of money, it would be nice to have something that will keep looking good for a long time. I think the O2ptima cover also does a great job of protecting the hoses, and it seems to contribute to the unit being streamlined in the water. (It may be psychology; I am no hydrodynamic expert!
)I think that the computers are well made though they are on the larger side. Most rebreather computers seem on the larger side anyway. On my wish list: I hope that they will move towards RGBM and/or VPM (I have been using V-Planner for over two years). I still like the VR3 as my top choice.
I think that the unit handles flooding well. You can fly it automatically or manually, and you can connect offboard gas to it. I have had excellent service from Dive Rite over the years, and I like the idea of staying with a major player in the overall dive industry.
Not everything is perfect. For example, I am not thrilled about using an Air II for reverting to open circuit though I can always resort to a bailout bottle (and even connect that to the unit using a standard low pressure quick disconnect fitting on the loop ). I hope that they come out with an open circuit valve on the mouthpiece as I have seen on other units like the KISS. I am guessing that this will be coming down the line.
Anyway, I have paid for my unit, and delivery is expected within a few weeks. I hope to start training in January. I will give a full report on the unit when I get started (and know a little about what I am doing
). I am psyched!
