The "internals" (MP hole included) are a system, can't say one size is preferred, as it all depends on everything else built into the call. I have used the sizes you mentioned, as well as others, they will all work if you figure out the exact combinations. And hole size does not in itself determine the pitch of the call, it will affect it, but other factors may push it one way or another as well. Trumpets look like a simple call, but they are actually complex little rascals to build, with a zillion potential twists and turns along the way.