I have both the SDB and 550. I much prefer the SDB for loading pistol rounds (which is all that it will do). It is a lot handier to work with.
Be aware that most reloading manuals are available on line. Go to Shooter's World, and do a search. I prefer to do a product search under 'Supplies, Reloading.' Here is the URL: http://www.shootersearch.com/productsearch_index.html
Also, join the NRA. They have a superb technical staff, and can answer any questions you have.
Good luck. Walt