RCBS, I have 4 different shell holders, all 4 are RCBS.
Then there are other difference between brands, the shell holder is a tool, I get all the use out of a tool possible.
There is a difference between the Lee and RCBS shell holders, I am the only reloader that benefits from the difference, then there is Herters, one fine shell holder.
(For me) The number one criteria for a shell holder is deck height, my favorite deck height is .125 thousandths, there is an advantage to having shell holders with different deck heights if the reloader knows there is a difference in deck height.
Then there is Redding Competition shell holders, for $40.00 dollars a reloader can have 5 shell holders that have 5 different deck heights, nice but not necessary. I purchases a #6 set at the Big Town Gun show for $5.00. I checked the deck height and found 3 of the shell holders were off by .001 thousandths each, again, they are nice but not necessary.