...
You also forgot the OKW Panther who just happens have very powerful vet4 and 5 bonuses.
The Comet is a good tank, but the Panther is much more cost efficienty, especially because the Comet performs very unreliable and inconsistent in it's role.
I Personally prefer Comet over panther...but they have different roles, one is medium tank the other medium tank/tank hunter...
OKW Panther cost more fuel than the comet...and vet 4 and 5 on Panthers comes rather late (if it comes).
Comet is superior in the following areas:
Smaller size
more rear armor
war speed comes at veto 0 and is superior to blitz...
non doctrinal smoke
White Ph. out ranges ATGs and kills them from far
Grenade kills ATG from close
More LOS
Detect invisible
Vehicle tracking
better R.O.F
Better accuracy on the move
More AOE
Less scatter
(generally better at flanking)