As Tim says both can be wallet busting if bought wrong
As I own both over for nearly 3 years
here is how I see it
993/ 97 (8yrs)
No rust ,suspension is more critical as its more complex , very fewer oil leaks happen,it is more an all round car than a 964 ,great touring car and and very capable on a track just feels a bit more weighty and better put together on the move ,you can leave a 993 for months it will start first time and never let you down
Note early 993 pre vario-ram my suffer from valve guide wear
964/90 (3 years) and my 2nd one
The rear quarters much more prone to rust as are the sills , engine rebuilds are not as common as you think ,yes they dribble a little oil but if they dont smoke on start up and on the move then the oil leaks are manageable over time but plenty of other annoying issues to get put right
964s hate not being used and will punish you with poor starting and hesitation issues
That said 964s are agile and very go-kart like to drive, not so good if you are doing a 300 mile journey in one
My 64 in the last two years has cost a lot of money replacing fuel and electrical parts and other failing parts but now starts first time every time and goes like stink
The spend over a three year period on a 964 has been far more than the spend on the 993 for a five year period
964s have rocketed in price but only the sorted ones and C2 are getting rare, they are more of a money pit than a 993 and the owners of 964 will have had to spend more on them to start with
Both are fantastic and rewarding in different ways
If I had to choose one to keep the 993 wins
8)