Real cabs are cheaper.
That's a bit of a broad statement.
On a cab per cab basis, yes. On a per game basis no way, not even a little. For an arcade environment it is a difficult balance to achieve I suppose. You could have 10 machines capable of playing 1000 or more games each, but the 11th customer is SOL. If you have dedicated cabs it has to be games people like. Good thing the answer has basically been handed to you... NO MAME FOR PROFIT. You may be best off with some cabs that run several boards. I suppose you could also use the boards that run several games, but I think those are legally sketchy also, I'm sure somebody will chime in who knows better, but I remember hearing someplace that the licensing isn't quite right on those.
Good luck with you business adventure, I think that it may be a good era for some retro arcades to start opening up, the age of people who were around during the boom is prime retail and amusement demographic, I would totally dig a place that was all about being an arcade based on the early 80's to early 90's experience. Most of us were too young to drink when we enjoyed the arcades the first time, but I think that a bar with this environment would do fairly well if it were done right.