Hey JonnyQ,
concerning your reasons, all 4 can be served by almost any CCR. Concerning point 4, gas cost must on CCR be mentioned with scrubber cost in one breath. My experience is that with increasing He costs it does in fact pay off, depending where you dive. Some remote locations will demand you to carry lime when flying in- this can add up to quite some charges for freight costs.
I chose to prefer active scrubber monitoring with self-packed scrubbers to safely utilize most material. (I dive rEvo with RMS) However, it really depends where you dive. I believe in most parts of US you may get lime for the cost of a softdrink- may therefore not be the huge advantage.
Concerning Point 1), both SF2 and rEvo are fully redundant. One often mentioned topic is that the shearwater controllers (used on both) do not offer any audible alarm feature. Its a hot topic sometimes- task loaded divers neglet their displays and miss warnings. The NERD may help a little- my opinion on this is that the fundamental rule of CCR diving is to know your PO2 at any point in time- with alarm or not does not matter.
Points 2) and 3) apply to both- SF2 and rEvo.
Point 4) was one of my critical issues as well, so far I am happy traveller with my unit, either checkin or carryon.
Point 5) is not easy to answer. The method of diving depends on your needs and skillset. JohnnyC said it already. For Photography however, a CCR allows you very close contact to marine life- other than making noise and bubbles- perhaps that could be the main argument.
Point 6)- Keep in mind the cost for training. My recommendation would be to do one or two 'discover rebreather' try dives before fixing your choice. CCRs can not be modified so much- your trim depends on the unit and the diver. (Skill, Bodymass) When casually testing and comparing you may even find out not to like CCR diving at all- if you like it then trying is better than guessing.
Point 7) was my argument not to chose the se7en nor to continue on the Evo. Both SF2 and rEvo can be full hCCR- meaning you can either do a fully manual approach or use the eCCR for convinience. I normally dive manually but having the shearwater controller serving as a backup well below my target PO2. Taking videos/photos even the tiny amount of boyancy change during O2 injection pisses me off- Perhaps (in accordance to my GF) I am just a control-freak who wants to be self-reliant...
Flood-recovery is often mentioned- not a point for me. This may depend on the diver- no unit however craps out on tiny amounts of water. When losing the loop you may have obviously other problems at the same time that will force you on bailout anyway.
All this said, be aware- you will learn diving from a new beginning on. Switching to CCR makes you an OWD with terrible trim and skillset
Its however worth all the trouble!!
concerning your reasons, all 4 can be served by almost any CCR. Concerning point 4, gas cost must on CCR be mentioned with scrubber cost in one breath. My experience is that with increasing He costs it does in fact pay off, depending where you dive. Some remote locations will demand you to carry lime when flying in- this can add up to quite some charges for freight costs.
I chose to prefer active scrubber monitoring with self-packed scrubbers to safely utilize most material. (I dive rEvo with RMS) However, it really depends where you dive. I believe in most parts of US you may get lime for the cost of a softdrink- may therefore not be the huge advantage.
Concerning Point 1), both SF2 and rEvo are fully redundant. One often mentioned topic is that the shearwater controllers (used on both) do not offer any audible alarm feature. Its a hot topic sometimes- task loaded divers neglet their displays and miss warnings. The NERD may help a little- my opinion on this is that the fundamental rule of CCR diving is to know your PO2 at any point in time- with alarm or not does not matter.
Points 2) and 3) apply to both- SF2 and rEvo.
Point 4) was one of my critical issues as well, so far I am happy traveller with my unit, either checkin or carryon.
Point 5) is not easy to answer. The method of diving depends on your needs and skillset. JohnnyC said it already. For Photography however, a CCR allows you very close contact to marine life- other than making noise and bubbles- perhaps that could be the main argument.
Point 6)- Keep in mind the cost for training. My recommendation would be to do one or two 'discover rebreather' try dives before fixing your choice. CCRs can not be modified so much- your trim depends on the unit and the diver. (Skill, Bodymass) When casually testing and comparing you may even find out not to like CCR diving at all- if you like it then trying is better than guessing.
Point 7) was my argument not to chose the se7en nor to continue on the Evo. Both SF2 and rEvo can be full hCCR- meaning you can either do a fully manual approach or use the eCCR for convinience. I normally dive manually but having the shearwater controller serving as a backup well below my target PO2. Taking videos/photos even the tiny amount of boyancy change during O2 injection pisses me off- Perhaps (in accordance to my GF) I am just a control-freak who wants to be self-reliant...
Flood-recovery is often mentioned- not a point for me. This may depend on the diver- no unit however craps out on tiny amounts of water. When losing the loop you may have obviously other problems at the same time that will force you on bailout anyway.
All this said, be aware- you will learn diving from a new beginning on. Switching to CCR makes you an OWD with terrible trim and skillset
Its however worth all the trouble!!
The main Shearwater is the controller and monitor. Should it fail, the CAN Bus takes over both jobs, though you won't see the status of the cells. Add a PDC to the Fischer cable and now you have triple backup. However, should the CAN Bus fail, then your main Shearwater can't control it, but the diver can. I haven't been told if the primary Shearwater would still be displaying cell info. Ergo, I have another Shearwater on the Fischer just to be sure. Perhaps 
