Pretty sure if Oscar was fighting the Anthony Stephens and Kevin Lueshings of the world he would have looked just as devastating.
Oscar. I believe his hook was most effective at lightweight though. Blinding speed and powerful, very sharp. My personal favorite example is against Ruelas, although my fave Oscar fight is Vargas and we all know Oscar dropped Vargas with the left hook. Obvioulsy Tito's hook at welter was devastating. I just think Oscar's left hook particularly at lightweight was perfect, and could drop any lightweight ever.
a toss up. both left hooks were equally powerful although tito had a more traditional left hook while oscar had an unconventional one....
I want to say Tito. Against most opponents, it was more of a stand-out trump card for him. But against similar qualities of competition, Oscar's seemed to perform quite as well. A past-prime Oscar dropped Mayorga with a single left hook, while a prime Tito landed two flush ones with not nearly as much effect (one could argue the difference in "seeing" the punch made the difference in the effect for each case, but still...)
I went with DLH although Im well aware of Tito's poison... I think everyone feared Tito's more, buy DLH's was a lot more effective. Tito would throw the left hook a lot....and miss the mark more than he found the Target. But when Tito did nail his Target the fight was as good as over. DLH was Sharp, powerful and precise with his hook.