As a process technology of course the 32 nm is better, but in fact there is hardly any overlap between the two in current processors (so you don't really have the choice):
-If you want a dual core intel processor then the choice is clear: 32 nm core i3.
-If you want a quad core intel then all are 45 nm (and they are good).
-If you want a six core intel processor (and can pay for it), it is a 32 nm processor.
As khicharkumar said, list your options and your budget to help you choose.