JasonB,
Did you notice any improvement in accuracy after using the crimp die?
In all honesty I never compared. I use their separate crimp dies for self loading rifles (also use their post size & crimp die on pistols) as a safety measure against set back on the feed cycle. All I can say for sure is the crimp the Lee die gives is far more consistent (and forgiving) than the RCBS combo seater/crimper I was using before.