I also have the VariXII 1-4X on my slug gun and like it very much. It has plenty of FOV and is plenty bright enough for any shot during legal shooting hours, and I hunt some pretty thick, dark pines sometimes. For deer to around 125 yds. it's perfect IMO. I don't know first hand about the VXI 1-4X, but I have an older 2-7X Shotgun/Muzzleloader Leupold on an Omega and like it too. All my scopes (10) are Leupold.
I think a good quality 20mm objective lens, like the Leupold's, gathers plenty of light and does a better job than a poor quality 50mm.