the vise size isnt as important as what its mounted to, 5" is plenty big enough as long as its mounted to something sturdy
theres a 5 inch vise in my basement mounted to a freestanding work bench, maybe once a year i use it hard enough that tools fall off the pegboard
the 6 inch vise at work is clamped to a 10 x 10 x 3/4" steel plate fab table … that vise will take anything you can throw at it because the table cant move w/o using the crane