I've had the 32's for 2 seasons now and absolutely LOVE them!! I've tried the 67's a couple of times now and would be a liar if I said there was a noticeable difference between them!
In my opinion the main difference is aesthetic, with the 67's looking slightly sexier!!!
Perhaps the 67's are a tiny wee bit harder to hit sweetly all the time, however if you are playing off of a hcp of 1, then ball striking is obviously not a problem.
Interestingly, when both clubs were available, Luke Donald chose the 32's!!
I'm going to pull the trigger on a set of 67's for the coming season, they are arguably the most beautiful club ever made!!!