I think of the two, the latter personality type makes a better president. Vivek is a rationalist who might not feel comfortable in highly chaotic, highly risky situations, especially if he is under some personal stress. Trump seems to thrive on stress like a classic Type-A personality. 'Not that Trump's psyche may be easily pigeon-holed as anything fixed - his adaptability  to new things is one of his fortes. 

Trump just has more experioence in life and of course, in the White House, which doesn't mean Vivek is not qualified, but it means he might be a better choice for VP if DJT is the nominee. 

DJT has stated however, that he currently does not foresee selecting any of the other candidates as running mates, and I believe him. DJT does not want to get burned again as he no doubt may feel he did by selecting Pence.