I believe a 9600Pro EZ is a 9600Pro in terms of core clock speeds, but has slower RAM.
9600Pro 400MHz core/600MHz memory
9600Pro EX 400MHz core/400MHz memory.
It's not really worth it, the extra bandwidth is quite important (look at 9600XT's, the core clock increase doesn't do much, the ram is the same speed, which may be fairly limiting)
The EZ is better than the non-pro, but not worth it unless it's a really good price compared to 9600Pro's.