The admirals all being top tiers obviously have extremely strong haki. More importantly tho they like everyone they specialize in a haki
Imo I think its likely that aokiji and akainu specialize in observation and armament respectively. Fujitora and ryokugyu as replacements are probably the same as
in general oda also seems to give the edge to armament specialists over observation specialists when duos are involved. Which does make sense but armament haki is more strictly combat focused than observation

Imo I think its likely that aokiji and akainu specialize in observation and armament respectively. Fujitora and ryokugyu as replacements are probably the same as
- Fujitora and kuzan both specialize in observation haki but use it very differently
- Aokiji probably having advanced intent sensing ska future sight
- Fujitora having advanced presence sensing probably
- Ryokugyu and akainu both specialize in armament haki but use it very differently
- Akainu probably havin barrier (they all do) but more importantly penetration armament
- Ryokugyu having some advanced form of armament that helped make his blade black maybe
in general oda also seems to give the edge to armament specialists over observation specialists when duos are involved. Which does make sense but armament haki is more strictly combat focused than observation
- Akainu > aokiji
- Zoro > sanji
- Ryokugyu > fujitora?
- Kid > law
- Etc.

