I'd like to ask people's opinions on a tactic I've observed other players using from time to time. I'll use the "Classic" map as an example. In the situation I've noticed, let's say a player holds North America with 51 armies. He, instead of deploying 15 armies on each his borders with his opponents (i.e. Mexico City, Anchorage and Montreal) and leaving one army on all the interior territories, will place an even number of armies on all his territories or at least leave three armies on each of the interior territories and put the rest on the borders.
I can imagine various strategic reasons for doing this (preferring to be in a defensive position rather than offensive, not wanting to appear threatening his neighbors, hoping to mask his strength, etc) but is there a mathematical reason for doing it as far as rolling the dice go? Is it actually harder for an opponent as far as the odds of the dice go to kill 51 armies if instead of having 15 on each border and one in each interior territory he has 3 armies on the interior territories and just leaves 11 armies on each border (or some other ratio)?
Again, I'm not interested in strategic reasons for doing this other than if anyone knows if there's actually better odds when it comes to the dice for doing this?
Thanks.