I have a '77 Hunter 33... I have no complaints with either her construction or her performance and I imagine the 30s were built and would perform similarly.
Things to look out for on the Hunter would be the holding tank (they used bladder tanks as original equipment in many of them; if it hasn't been replaced already you'd probably want to do so), the mast step, and the binnacle/steering quadrant mounting. For the latter two items, the original installation was done with plywood reinforcement; a lot of them have since been re-done with solid fiberglass but if the one you're looking at hasn't, again, it's probably something you would end up doing (or regretting not having done
I don't mean to sound negative, those are just particular things to look for. My boat had most of those refits completed by a previous owner, and I'm extremely happy with her. Points well, reasonably comfortable at anchor and under way, and easy to handle in most conditions.
Not to plug a competing site or anything, but Sailboatowners.com has a LOT of owner reviews for both Hunter and Catalina models of all vintages... it's worth a read through them for the models you're looking at to get a feel for what common complaints might be.