I've owned Lee, RCBS, and Dillon. After being able to compare all three, the only two I still own are the RCBS and Dillon- and the RCBS has been gathering dust since the very day my Dillon got bolted to the bench.
Precision, ease of use, and QUALITY are the big factors to me. I'd equate it to the difference between a Chevy and a Cadillac. Less plastic, and better workmanship. Pay more to get more, IMHO.