Looking at the data sheets, all I can determine thats different is that one is an inline 4, gear ration 1.86:1 and the other is a v6 gear ratio 1.75:1.

Can anyone tell me which is the better motor? and Why?

VF motor quieter. Much better low end thru mid range performance. Big bore motors will not have to work as hard as the 4 cylinders.

What are you putting it on and how is boat primarily used?

Tidewater 2110, mostly lake fishing, but it will hit the salt a couple times a year

Based on your boats weight, I'd probably go with the VF model.