Is there an accuracy advantage / disadvantage of 1 piece bottom metal over 2 piece ? I am not looking for additional cartridge capacity. It does seem as though the 1 piece is slightly less time consuming as to reassembly.

Yes the 1 piece will take 30 seconds less time the 1 or 2 times you will ever have to assemble it.

I happen to prefer the 1 peace for me just easier. I wouldn't pay major $$ to get one over the 2 piece. Some will say there is a chance with a two piece to over tighten the middle and warp the action from an accuracy standpoint.