I use more than one manufacturer simply because different manufacturers excel at different calibers. Example, I like The RCBS Competition micrometer head front load bullet seater in .223 (because I shoot comp 100 yard bench in .223.... However, I prefer Lee pistol dies and I have some Wilson's and some Redding as well as Dillon Precision which you don't even mention....
I've used Lee, RCBS and Lyman. I've not seen that much of a difference in these brands, so I tend to go with the least expensive. Perhaps, if I were doing more match shooting and being more particular about specs, I'd choose a different brand.
However, I'm having good success with my current Lee brand dies.
__________________ If God didn't want man to eat animals, he wouldn't have made them out of meat.