Definitely get the RCBS lock out die.
The Hornady die just indicates where the powder is. You still have to be watching it.
The RCBS locks the press down.
When I first started reloading 9mm with my LNL, I had everything set up perfectly and was going along just fine when all of a sudden the press locked up. I knew I hadn't missed a round with the powder, so I start checking everything to see what was binding.
Finally, after at least five minutes, I checked the case under the lock out die and it had no powder. I would have bet you a thousand dollars that there was nothing wrong with any powder in any of the cases.
If I hadn't had the lock out die, I would have missed it.
Still to this day I don't know what happened to cause me to not charge that case, but I did, and it caught it. Kind of scared the hell out of me.
I will not run my LNL without that lock out die in place and set.
It's frustrating to set up the first couple of time, but keep trying until you figure it out.