I've built 3 computers in HAF 932's and 3 in HAF X's. I prefer the HAF X. It looks much cleaner inside and I found it easier to route/hide cables. Both cases are big, so I wouldn't really buy based on the size of one vs the other.
I haven't done any side by side comparisons for airflow or temps, but both were very reasonable.
If the extra $40 is a concern, you'd be fine with the 932 BE. Both are great cases.
CM also sells some refurbed units that might get you a case for a few bucks off.
CM Store