They're both good. Them and the Hornady or Dillon are too. RCBS seems to be more popular, and more people have them. But I often think its only because RCBS is more agressive at selling their products, and more dealers/distributors carry them, which makes them easier to find/buy.
As far as quality, I doubt there's any difference.
Now, I do really like my old Hornady 007 because the opening is offset to one side a little. Being left handed, its easier and faster to get cases in & out of it. A Rock Chucker fell into my lap a few years ago, and I use it; but I sure prefer the old 007.
Nothing wrong with Lee carbide dies either.
In fact, they forced the industry offer and sell them at something lower than the price of a new Cessna when they brought them out in the 80's. I've had 'issues' with their bottleneck rifle dies, but I use the heck out of their carbide dies for .357 & .45ACP.
I don't know how many spent LP primers are in a gallon, but I collected a full gallon of them under my Pro-Jector from loading .45ACPs over a few years. They all passed through the bottom of a Lee carbide sizer. And its still on the job too!