I actually went back and looked up one of my old threads.
Per it...
Tony Williams ranked the Hispano round at 201 "damage points". The MG151 HE round was 110, the AP round was 109, and the Mine round was 236.
So the HE and AP rounds are ~55% as effective as a Hispano round, and the mine round is 117% as effective.
In other words, my first guess was pretty close... so I think even if they modelled the rounds individually I think you'd end up with my first post, not something dramatically different. If anything, the LW guns would be a little bit worse overall if individual rounds were modelled, if the modelling was done in accordance with Mr. Williams measures.