I really don't have a round count on the press other than to say that it was many thousands. The original leverage system was lubricated by means of weep holes through which you could apply oil with a needle oiler. The first replacement set of parts had been modified by the addition of more weep holes for lubrication, and that is where I'm at with my two 550's at this point. The photos I've seen of the latest 550's show that they now have grease fittings like the ball joints on a vehicle back in the good old days. Adding grease under pressure like that should bring about a huge improvement in tool life.
As far as comparing the 550 to a Hornaday, I just don't know anything about that press. If the leverage system is made of iron or steel rather than aluminum like the 550, that should give it a huge edge over the Dillon, but I have an RCBS Rockchucker that I bought new in 1981, and I had to rebuild the lower end on it after about twenty-seven years, and it is made of iron.
In my opinion all compound leverage presses, regardless of material, should have provision for lubrication with a grease gun due to the forces at play, but then I'm picky enough to wish that the car companies would again build cars that have greaseable suspensions, something which is not likely to happen again.