I have and use both. I think for all out speed and ease of use, I favor the Lee, I also think the feel is better with the Lee. After a few thousand rounds (probably 6-8000), the plastic bushing that surrounds the shaft that seats the primer gets oblong and starts hanging up. Then it's time to replace the unit. Luckily, you have different parts for small and large primers, so if you reload both, you have to reload a lot to wear it out (I've worn out one for small and one for large over the last 5 years).
I bought the RCBS because there was no way to use the Lee to prime the 408 Cheytac case (338 Allen Mag). In fact, I had to modify the RCBS so the 408CT shellholder would even fit! So I just leave it setup for the 338Allen mag and use the Lee for everything else.
Unless they've changed the mold, you need to open up the area around the shellholder on the Lee to fit the WSM size cases (2 minutes with a dremel and you're good to go).
The one thing I don't like about the RCBS is that the 'push rod' that actually seats the primers can fall out or easily get misplaced as nothing holds it in. Nothing like that is loose on the Lee. Also, switching shellholders on the RCBS is slower, as you have to remove a nut and the safety bar to swap shellholders (the Lee takes about 5 seconds to swap shellholders, but it doesn't use standard holders).
Cost wise, the Lee is really cheap but you need the matching shell holders (get a kit that fits most shells for $13 or so).
Overall, I like the Lee and recommend it.
If some is good and more is better, then too much is just right.
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