I just did The Knot (I think I'm allowed to call it that now) for the first time over the weekend. There was some hairy current, but i was under water for 5 hours (5 dives, one of them 11 minutes as my buddies got blown off the down line so I aborted.) I did bring 2 extra 3l RB bottles. It probably wasn't necessary to switch bottles between days but I have them, had them with me and it took 5 minutes. The limiting factor on the CCR was moved from gas to thermal comfort and "how much drifting deco do I want do." It depends as much on the dive boat and what they're comfortable with. Dive boat logistics get complicated even if everyone is on CCR. Just because you can stay underwater longer, doesn't mean it's always a good idea.
I have a rEvo because it seemed like a popular unit and 4 years ago it was what my friends were diving. It's what Mel dives. I bought a buddy's unit, used and just recently purchased a brand new one. (Old one is for sale!
I'm not the right guy to talk to about how to select a unit but I think it's important to think about service and who you will be diving with. It's good to know that if something goes horribly wrong, your dive buddy knows what button to press and how to "rescue you."
Around here I can say I see rEvos and Megs. I've also seen an Evo in the water some KISS but that's about it. rEvo service maybe be in New Jersey but it is very end-user serviceable unit. You generally don't have to ever send in the whole unit (or the head, since there isn't one.) I've had some issues with electronics but have had wires and handset fixed locally and depending on what redundancy you have, you can just remove a part, send it in and keep on diving.
I tidy up the rEvo and and put what amounts to a grill cover on it and wear it on airplanes as a carry-on backpack. Travel is limited to places where I can get O2 fills. 85% oxygen is probably as low as you want to go for your O2 bottle. This is important to find out before you book a trip. Most dive shops that think they know everything about rebreathers think you can just slap in some nitrox and call it good.
I love diving CCR, much better interaction with critters, warmer, quieter, I don't have to worry about a $200 trimix fills, I don't have to walk around with big steel doubles on my back. I don't have to move big doubles in and out of the car for diving or filling. Time saved by lack of gas twiddling is replaced by electronics twiddling and sanitizing. I do longer dives when possible.