Oh .. Come on really?
SM a fad. That's a foolish statement. I'm sure some people do get into it because it's the latest and greatest but still.
If I had to choose I'd choose SM over doubles every time. With SM you just have two single cylinders to lug into the car rather than some Manifolded twins. It's pretty easy to pick up a couple of tanks from your stock and put them in the SM slings rather than setting up a pair of manifolded twins, which you'll generally keep rigged as dedicated units
At the end of the day you still have two cylinders and the same gas and similar redundancy (obviously a manifold has the advantage here)
And if your on a boat thats off to a 40m+ site everyone (except the foolish) are going armed with multiple cylinders of back gas and deco etc. so they're prepared for that. Does a SM rig take more space than a twinset?
I love the way SB gets bent out of shape about the silliest things
I agree that SM is not a fad. But, SM every time? Not me. There are times when I think each one has an advantage. So, I'd pick one depending on the specifics.
Most of the time, for me, I roll up in the parking lot, put my wing and BP on my BM doubles, stand them up on the tailgate of my truck, put them on my back, walk to the boat, sit down in my bench spot, and shrug them off. It's a lot easier than carrying 2 individual cylinders in my hands. My friends with SUVs do the same thing, so a pickup is not a requirement for this.
Also, I use 120s for BM doubles. I think the 120s are probably too long for me - and certainly too long for some people - to use as SM cylinders. I am using 100s for SM. So, it seems to me that there is an advantage to BM doubles in terms of the amount of gas you can carry (conveniently). Most of my tech diving friends started with BM 100 doubles and most of them seem to have eventually concluded that 100s aren't big enough for the tech dives they want to do and have gotten themselves bigger cylinders. Going bigger in BM is no big deal. Bigger in SM does seem like it has the potential to be more of a problem.
And, if you are carrying 4 cylinders (2 bottom gas and 2 deco gas), which is really easier to deal with in the water? 2 on your back and 2 on your left side (or even 1 left and 1 right), or 1 on your right and 3 on your left? Sure, you can do it in SM, but it sure seems like it is EASIER (in the water) with 2 on your back. Maybe I'll change my mind on that when I am more experienced in SM.