I've used them on both. Very different animals BTW. A 330 is more like most Gibson jazz boxes. The flatwounds add instant boom and thump and a classic warm jazz tone. On a 335 they add some more oomph and the top end suffers IMNSHO, because the 335 is closer a Les Paul than a jazz box.
I'd keep flatwounds on a 330 and round on a 335.
I absolutely love the Thomastik Infeld flatwounds. ( Even though I usually replace the gold colored thinnest 2 strings with D'Addarios.)
I've been using D'Addario Chromes (flats) 11-50 on all of these guitars for years. Never tried the more expensive brands. I'm sure they're good, but I don't feel a need to change.
My Strat is the only electric that I have rounds on.