In their primes (by most accounts, Margarito is slightly past his,) DLH by fairly comfortable decision. Now, looking at how bad little Forbes banged him up, I think Margarito stops him late, TKO not KO.
Prime Oscar wins by a wide score, maybe even with a late TKO. I think a current matchup would be fascinating though. Tony might be able to overwhelm him if he could keep his punches slightly more calculated, thereby avoiding repeated counter left hooks.