I prefer the vivo because it's a more sturdy feeling seat in general, the deeper headwings make it great if the kid nods off (out of my 3 kids, only one slept fine in the turbo... I know that's not the average, but that's my kids... deep headwings were essential when possible)
I also like it because it sits so low that it fits well in third rows, it's never tippy, and it's more padded and the cover is so soft.
However, the turbobooster is and always has been a default great choice and a go-to for boosters.
The Vivo goes a little taller, but not enough that if money is an issue I'd push it. One other reason I got the vivo was because it has a shallow seat pan. Ruthie was ALL torso for so long that most boosters (turbo included at the time) were too deep for her to have her knees bend at the edge. The vivo was the only highback at that time (now the oobr that came out later would have been good, but way more pricey) and still is the only one that I would be able to afford that her legs fit well in. So I think it also depends on how he is built.
if he's leggy, I would go for the turbo or maybe the harmony dreamtime, which offer more leg support.