catalina 34 Mark II or catalina 350
You need to remember that Catalina''s tend to be bigger boats in general. Our 36 MKII is 36''4" LOA plus the pulpit overhang or almost 37''4". The 350 is 35''6" LOA plus the pulpit overhand so I bet it''s 36+'' and I am sure the same holds true of the 34. From my experience 34+ years of sailing once you adjust to any of them the size won''t be a problem, I am sure they all handle differently, to see what you like do some begging at your local marina or dealer. Where you will see an apparent difference and may require some adjustment will be docking. Obviously the bigger the boat the harder to do, but that too pass'' with practice.
As for what to buy, you need to check your wallet, I am sure the 350 has a much more modern systems approach than our 36 or the 34,is it better I don''t know, but probably better layed out from a convienence standpoint. But as someone mentioned 30K more that a late model 36 MKII and probably 45-50K more than a late model 34.
As I said, go sailing and give them a try.