It is a 650 for me. Yes it's primer feed system is not case sensitive, it will feed primers with no case in position. This does happen occasionally, but if you are watching it is not a problem. I don't use the low primer warning as I load 100 cases at a time, in the interest safety and quality. 100 cases and 100 primers go in the machine at a time and when that is done, another 100 go in.
I fine gent I met at the range allowed me to load on his SDB, 550 and 650 presses and I went for the 650. I have never loaded on a LNL and I'm sure you would be well served with either.
I have Dillon dies for 38, 357, 9mm and 45, for the 44 mag I have RCBS dies and I don't like them. I like the three die Dillon easy to take apart with out loosing adjust and I like the separate seat and crimp dies. I do not like the RCBS 2 die set with the seat and crimp in one die.
I do like Green Eggs and Ham