Removed the extra to focus on the two that I know the most about. The Lock N load is not near the press the Dillon machines are and I would strongly consider saving for a 750 if you feel you have to have the feature set. My dad uses a lock and load and I have loaded several thousand rounds on it, the press is far slower than the 550 without the case and bullet feeder and not much faster with as it just doesnt handle the cases as well as the dillon machines. I have personally owed the following: 550/650/1050. I still have the 550 and the 1050 with autodrive. If I didnt need to load 40k rounds a year of 9mm for competition I would probably just have a 550. Its best feature is how simple it is, while still being plenty fast. I could have a new loader running it at 400 rounds an hour in no time and making quality ammo. I firmly think its dillons best press.
I dont find the need for powder cop or lockout dies and do not use them, with the 550 you look in the case before you index and do it with your thumb before you set the bullet. If you somehow forgot to index there should be a bullet already seated on station 3. The best way to prevent mistakes is never leave the shell plate down and full and if you need to step away leave the shell plate up so you know exactly where its at. You will never outgrow a 550 and it will load any caliber you need. While set up how it should be is around 700 dollar thats nothing compared to current ammo cost. Always buy primers at least 5k at a time and pistol powder in 8lb jugs once you know what you need to keep cost down.