Dusty Miller:
I've followed this forum for quite a while and have yet to see a really authoritative answer to your question about comparing the three. What appears to happen is that people pick the one they think is best, develop a brand preference, and stick with that brand. But one thing is certain, there are a lot of guys (me, for example) that have a Rockchucker as their single-stage press and a Dillon 550 as their progressive press. I can understand why they are as popular as they are. I've had the Dillon for about three years, use it for my 45ACP and nothing else. Everything else gets done on the Rockchucker.
I think you should refine your question around specific features that interest you. For example, specifically how do you need to modify the machine to load two different cartridges (like 45ACP and .223)? Specifically, what are the steps in changing the machine to use a different primer size (small to large and back)? How do you empty the powder from the powder measure after a loading session? How clear is the documentation on troubleshooting? Then decide after you have answers to the questions that are important to you. The manuals are probably online, so you should be able to evaluate each based on their operation and setup. After all, their good customer support is a given (except, in my limited experience, with Hornady. One experience was enough.) They are all made to last. The functionality is the same (i.e., they all are designed to do the same thing.) That leaves features and operation, which you can learn a lot about from their manuals.
Not having been through this exercise myself, I would be interested to read your results. By the way, the examples I gave about what features to look for were not idly selected. These are important areas that you will want to scrutinize carefully.
My own decision was simpler. We have a Dillon retailer near here and he demonstrated the 550 for me. I liked it, saved for it, bought it, and have been happy ever since.
