Traditional rules of fashion would make the case for the following, in terms of formality (all balmorals):
2 captoe (straight tip)
3 captoe (perf tip)
4 captoe (madallion toe)
For the first 3, the differences are negligible. All 4, IMO, can easily be worn with suits. Number 1 is the least versatile (I used to own the black shell plaintoe bal on the Aberdeen; they felt out of place unless with a Suit) . Number 4 is, obviously, the least plain.
I can understand this, in which case, perhaps a plain toe blucher is more formal than a cap toe blucher.