The rear stays on a MTB bike are spaced wider than a road bike to accommodate a wider tire. That also impacts available clearance for larger chain rings on the inside smallest ring. I can't myself on my set-up. If you don't currently have clearance with a MTB crankset to go to a larger size, moving to a road crankset won't change that. Otherwise I personally don't see an issue or an advantage either for that matter.

Do you really think you can push a 51T on that bike to the point that it'll make any real difference over swapping just a few chainrings and running a 22-36-48T?