Actually, the reason Arrow/Vekomas are so rough and Beemers are so smooth has nothing to do with inside/outside guide wheel arrangement. It has to do with the transitions, and the fact that B&M wheels can individually steer, and are spring loaded to keep them against the track, resulting in a non existant gap between them and the track. The reason B&M uses outside guide wheels arrangement is that the track can be made cheaper like that.
On the other hand, Vekoma and Arrrow trains aren't spring loaded, and are barely articulated. And are thus very rough. The reason they use an inside guide wheel setup is because it was designed for small coasters where it would be cheaper to use a more expensive track setup with cheaper/easier to maintain trains.