Well generally when I stay beyond 30bb I am staying because I enjoy the dynamic of that particular table, be it a big fish / weak regulars, and that in itself generally lowers variance. So, I wouldn't say having a large stack is more variance for me... but in a vaccum if you gave me 20bb or 30bb or 40bb against the same set of good regulars, I think variance would be higher as stack sizes increased in a linear fashion.
I definitely feel it's easier to grind out hands/VPP's when leaving at 30bb. But better for my winrate if I stay around longer (as long as I'm playing my A game, if not it can be worse for my winrate to stick around beyond 30bb.)