With the acrylic, you can buff out that scratch, with glass it will be there for eternity.
The acrylic will probably be easier to get, and have better clarity- even when compared to starphire.
You are right, 10' sheets are fairly common, but get your wallet out for anything bigger!
I'd give at least a 6" mounting flange on a panel that big. We built one and used 1/4" 316 SS concrete anchors every foot or so. Drilled the acrylic (slightly oversize holes for getting the heavy sucker in place) for the bolts, sealed the heck out the flange and bolted it up with large fender washers. Then we coated the nuts and washers with epoxy. Never ANY drips or rust.
BTW, we epoxied the whole tank before glazing it.
HTH
Chris