I have been debating which cases to build my next motor on as well. If you talk to any of the engine builders on here they will all tell you you are giving up horsepower with a single carb. Even saying that I am still planning on building a set of x cases with ported cylinders using a single 46.
I am wanting something easy to tune and less parts to go wrong. I am personally willing to give up a bit of upper rpm power for a stupid simple setup. X cases are also a lot cheaper to get your hands on.