I have both a SDB and a 550b. Either will load a pretty good amount of ammo. I leave the SDB set up to load .45 apc with large primers and the 550b is used for everything else. The 550b will allow you to also load rifle ammo if you are interested in that aspect. The 550b also has a better leverage advantage to make loading less work. If you really want to produce a lot of ammo the 650 with case feeder is the way to go. You can load easily 300 rounds per hour with either the SDB and 550b. You can load at least 500 rounds per hour with the 650 with case feeder. Those are not the max. rates these presses can be used to produce ammo by any means. If you have plenty of time to reload you can use a turret press to load 1 to 200 rounds per hour.
The SDB will only allow you to load certain pistol calibers.