Why are there grooves in boollets if the smooth-sided design is effective? I load 9mm and 38 Special. Sometimes getting the roll crimp in just the right groove is a pain. I would think that smooth-sided would allow the crimp to make its own groove. I see many mold makers make boollets with many grooves while others do not. Why? Is it just marketing or is there a functional reason (under what conditions will each type perform better?). Is there a reason why one style is better than the other?