If you don't use three globes, some area ends up on the edge where it's hard to see. You generally need North America, Europe, and East Asia to all be clear enough to differentiate cities and countries. That's very hard to do with two globes. And two globes doesn't give the design interest or "tension" you get with three that extend outside the box.
I think it would seem odd to have one of the globes at larger scale than the others, to more clearly show Europe. In those situations, it's sometimes better to do three or four maps (as opposed to globes) at different scales, and use some clever graphic design device to integrate them. For instance, you could nest together four or five hexagons, each with a different map enclosed in it.