Speed isn't everything, but if I fill all ten of my primer pick-up tubes (about a minute each), keep components and acro trays close at hand, have brass lubed and 'ordered' on several large cookie sheets (400-600 rounds each) work from a known load on tightly torqued dies, under good light and have no interruptions, I can generate 900 to 1000-45acp rounds per hour, 750 to 800-9mm rounds per hr (I got fat fingers), 700 to 800 38Spec/357 rounds per hour, and 650 to 750 223/5.56 cartridges per hour.
This is checking charge weight every 20-30 rounds, OAL every 50 or so. I also use Wilson case and cartridge gauges-that helps a lot! Drop, check, go.
Cases must be clean and I have a compressor to blow out any dust or particulates that may accumulate on or under the shell plate.
To change calibers, speed depends on how much you invest. With a complete top-side it takes about five minutes. To add a powder measure to a set of dies in a toolhead takes about a minute, but setting the charge weight slows things down-10-15 minutes. To completely assemble dies to tool head then add the powder funnel, adjust all and tighten can take upwards of an hour.
The 550 is manually indexed-left thumb advances cartridges from station to station-it's faster to do then to describe but parts must be meticulously clean for proper function (air compressor!). The 650 indexes as part of it's basic function. Visit the Dillon site and get manuals for both machines for the rest of the differences.
I've got two 550 on my bench, one set for small primers, one for large---this is pretty typical. On calibers I shoot the most I have complete top-sides. for the others I have a couple extra powder funnels.---this is also typical. I don't have any extra Dillon bells or whistles or alarm systems except the low primer buzzer which is standard. I do have micrometers on the powder bars and the tool heads devoted to rifle rounds are bolted to the machine-both are 3rd party upgrades from
http://www.uniquetek.com/
Currently one press is doing 45acp the other 223/5.56.
I like my Dillons, the older has almost 900,000 rounds loaded (shot IPSC for about 10 years), the younger about 350,000. I've completely rebuilt the older press from spare parts kits and simple begging at the tech support phone line; took about 4 hours. Now it's as tight and smooth as it's younger brother.
You will need to make your own comparisons because I don't have any other progressive experience--well I had a Square Deal too, but it's at my sons home now.