I'd suggest it's not about switching regs. Switching regs is trivial. BM doubles involves lots of reg / gas switches anyway. If you aren't comfortable switching regs SM and BM doubles are both bad ideas. For that matter diving may be the wrong recreational activity.
The key advantage to manifolded doubles is most failures, including the most common failures, allow access to *all the gas*. (There are of course a few, vanishingly rare failures, that can cause the loss of 1/2 the gas volume.) This advantage is achieved at the "expense" of more failure points, and more opportunities to screw up the management of a long list of possible failures, all of which are behind your head.
The advantage of independent SM bottles (no manifold) is far few failure points, and the diver can put eyes on the problem. This is achieved at the "expense" of single failure preventing access to 1/2 of the gas volume.
Pick your poison. Key to risk management is understanding the risks you are taking.
Tobin