I chose 54 for my first deer rifle, because-even though a 45 would kill nearly every deer i've ever shot with any weapon, it wouldn't reach them all. And not that a "trophy" deer ever presented itself outside of my range, yet. The time is coming and I trust the heavier ball to be effective at a greater range, provided i do my part in knowing the best load and getting off a good shot-in that case.
Smaller bore, shorter effective range. But that one "step" between the most commonly available offerings is really only a half-step. That's how i sum it up. That there's just not much diff in .04-.05 caliber "upgrades" but that it takes .08-.10 difference in calibers to make a stink.