Well some users have claimed clockwork not completely wiping when you select wipe. Also the dalvik is located under advanced -few extra clicks-
On amon_ra, you don't need to worry about edify or amend scripting, as it accepts both, unlike clockwork 3.0+. If you were to flash an amend package on it, you'd get an error [on clockworkmod]. Also, on amon_ra, all the wipes are under wipe, neatly laid out, ect.
People tend to have less issues on it, but personally never had an issue on clockwork.
Since I'm using CM7 as my daily and dabble in other ROMs for fun, I mainly use CW now. It ultimately comes as a matter of preference.