Whoa, calm down. Vercetti is no better. (HUEHEUHUEHUEHUE) I said it. Vercetti is no better than Trevor.
Ha ha ha ... Firstly, GTA Characters portrayal is limited to the story or the game world revolving around them, made with the imagination of the writer with some real world inspirations thrown in.
So, who's better (as in gameplay wise or players option to fully flesh out his role) than whom isn't the question.
The right comparison comes with why one's more likeable (strengths, appealing quality, etc you count as impressive in the long run to be remembered) than the other. Vercetti beats him easily here.
This leads to next point, they are both separated by the ERA and the background (I'm sure Vercetti comes out much better than you believe esp. for the controversy stirred up after release by GTA V)
Next, the game ending, if you get my point here without obvious spoilers .. lol
I'll point out more, once story modes are released for the unseen portions in the game and as the topic asks something else won't derail it further.