If those are your only choices, and building your own isn't much of an option, then I would go with the Marshall. It's fairly large for a 2x12, so it should sound "bigger" than the others. It doesn't have V30's though. It comes stock with G12T-75's. Not a bad speaker, but the mids are scooped a bit, and the top end can get a bit fizzy and ice picky. The V30's have a much more focused midrange. If you do get this cab, one thing you might want to look into is swapping out one of the speakers for a V30. A combination of the two would probably sound real nice. I believe Bogner uses this combination in their 4x12 Uber Cab.

Building your own cabinet can be as easy or as hard as you want to make it. Only basic woodworking skills and common sense are necessary. I've attached a plan for a 2x12 cabinet I designed. It was designed to fit under my 5150 combo, so it's a bit oversized. The measurements are in inches. I left off the speaker hole diameter because different speakers require different sizes (usually all similar though).