+1 for the 80mm. I use one of ARC's precision machine vices (type 3) for 95% of the time on my WM14. I've got a slightly larger & heavier 'economy' vice for odd times I need extra capacity.
As is often the case, a lot of it depends on what sort of work you are holding the majority of the time, just don't get anything too big – they will get in the way with this machine and it's limited table size and clearance.
regards Mike