I have both the Hornady and the Sinclair. Both are good, both work. The Sinclair gives higher readings as it measures rounds in a different way. I have been doing some comparative testing between the two and need to finish and publish it.
Yes, the Hornady straightener function works easily, but I don't bother w/ it unless the concentricity is >.025, which is almost never. Unless you shoot at =>1000yds or do benchrest, don't worry about getting one, The newer sleeved seating dies by Redding and Hornady do a fine job of seating the bullet straight.