It's almost certainly going to be Vance's to lose barring a drop in popularity by Trump or a major mistake by Vance. The best choice for VP for him would be DeSantis by far but he may go Rubio. DeSantis would be the best choice for the top of the ticket in terms of actually doing the job though and I have little doubt if they had a debate he would crush the other 2 just like he did Haley and Newsom.
I like Vance but he hasn't actually done anything. He was a Senator for 5 minutes and a great bulldog cheerleader for Trump. Rubio has done a great job as SoS but he's a pure politician in the end, make no mistake. Lots of questionable moves in the past though.
Still any of them are great options in any combination. I'd love Kim Reynolds as well on the ticket, she's fantastic.
"The most terrifying words in the English language are: I'm from the government and I'm here to help."
Ronald Reagan