Honest question; but what makes you favor having them like this? Pros versus cons?
I like having the gauge tight to the first stage. Checking "at a glance" is not exactly accurate, since I do have to pull the tank out of my armpit. When I grab the tank to do this, I'm generally grabbing the valve, so when I pull it out on the bungee to check pressure, the gauge is right there by my hand, rotated so it faces me.
Pointed down along the tank, the SPG is further out of my range of vision and requires an extra grab to check it. And I don't like the clutter of having the SPG stick out "lollipop style" in some other direction.
I assume you originated in backmount - and were used to stowing the gauge on your left-hip d-ring, where it wouldn't be "at a glance". Or did you clip them up to the shoulder straps etc for the same benefit?
I use a standard hip clipped SPG on my backmount rig, and I'm fine with it. Sidemount doubles require much more attention to gas pressure: there are two tanks and SPGs, and the need to switch sources every 500psi to keep 'em balanced. That's why this is a great discussion, the more efficient this process can be, the better.
Also, when rotating the 1st stage to offer convenient SPG routing, doesn't that also make your other hose routing less optimal? I'm assuming, again, that you must be using a top-mounted inflator - as a bottom mounted inflator, run from the 1st stage 5th-port (end port) would mean the LPI hose was routed down to the belly - screwing up the LPI stowage.
I use an LP manifold, so I only have to worry about one LP hose on the first stage. It routes down along the tank, under the stage bungee to near my hip, then up along my shoulder strap to where the QC-6 connects. All the rest -- short hose, long hose, BC inflate, drysuit inflate -- are connected to the manifold between my shoulder blades.