Best AB workouts?

[YoungGunsNY]

Hey guys - I been running a diet for 6 weeks at roughly 3700cal/480pro/230carb/90fat .. I'd say I'm packing on lean muscle through my eyes.. since I've been dieting these 6-7 weeks without cheating and no drugs/alcohol .. I notice my abs getting more and more defined every week. However, abs are controversial - people say you can work them everyday/other day and some say to train it once/twice a week like its a regular body part. I'm currently following the Pendulum Bodybuilding Workout -in 2nd week- posted in the sticky - and just wanted to get some veterans opinions on the abs. What workouts are best ? regular crunches..medicine ball crunches.. machine crunches..? thanks