I have two 550's and an unmodded 450 since the early 80's and they make 100% reliable ammo as fast as I'd make them on any other machine on the planet because I take my time.

So, a 500 or? Dunno, if you have the coin, you're in a hurry to make a lot of ammo and want an impressive machine either will make great ammo, or junk as it happens.