My thought here (being a 550 fanboy)
The qusetion you have to ask yourself is
"Do I feel lucky"
No thats not it. I reload a lot of off the wall outdated and or military rounds. So far my 550 has been doing it and a caliber swap in quik & easy. But if you only load a limited amount of calibers you might not need it.
The only thing better than a 550 is two 550's, one in large primer and one in small.