As far as I know, Collagen starts to break down below 60°C/140F, time play a big role, i.e. to get the same breakdown at 60°C as 80°C you might need 24-48h instead of 3-4h.
The higher the heat the more the meat is contracted and it will get dryer, in a stew that might not be as obvious as in other cooking methods but it should still be the fact. Compare tough cuts of meat cooked sous vide at 55°C-60°C for 24-100h, they get very tender and moist.
So the benefit will be moister meat. I think you must cook the veggies at much higher temperature (80°C-95°C) so you would have to separate the two. If the end result is worth the effort I do not know, I have wanted to try doing a 'stew' with meat cooked sous vide at 55°C - 60°C for 24h+, with the veggies done on the side at 80°C-95°C, normal stew style, to see if it would be better, but I have never tried.