I really don’t see how you could go wrong with either one. I have a 650 and 2 550s , I tend to use the 650 for 45acp and 38 special and most often use the 550s for rifle calibers. I have multiple tool heads and have 1 550 set up for small primers and the other set up for large primers . It takes less time to change calibers on the 550s , but the 650 loads faster. My real world load rate is about 300 to 350 rounds on the 550s and somewhere in the 5 to 6 hundred round per hour on the 650. I don’t find that manually rotating the tool head is a problem on the 550s and prefer it for rifle calibers. DHS on centerville road has in the past held classes in their loading room on Dillion equipment you might contact them to see if they still offer these classes. I can’t think of a better less expensive way to find out which loader you’d like the best. As I said at the start of this post I don’t think you can go wrong with either Dillon that you pick.