A couple of points...
a. In some calibers...with some powders...( now I realize you can pick a powder that is higher volume) ....but with some common powder the Min is only 0.4gr apart from the Max....and there is no way you can see that with your eye. You need a powder check to catch that .../ my powder check die on most powders/calibers will pick up a 0.2gr variation.
You can inspect for a no drop with your eyes / maybe install a small mirror to help...
b. 650 press or any press that auto indexes doesn't sling cases around causing issues.../ it will if you don't adjust it properly ...but that's a matter of just adjusting the press properly.
c. auto indexing is safer...because it removes one human error issue /forgetting to index / or indexing without powder in the case...manually indexing is not inherently safer / it adds another step - where a mistake can occur. A manually indexing press is not inherently dangerous either ...no matter what press you use - you have to pay close attention to what you're doing.
d. a 550 with a case feeder and a 650 with a case feeder do operate at about the same speed / but the 550 is a little slower - because you have the extra step of indexing the shell plate...its only a couple of seconds...but it still matters. There is no way a 550 is ever faster than a 650....the 550 has an extra step ...it can't be faster ( and I've used both ).
I have buddies that have 550's and SDB's - one has a 1050 ...and a few of us have the 650's ...and some use the LNL - others one of the RCBS presses etc....and all of us turn out safe and consistent rounds --- because we are careful of our procedures, keep our presses in good shape and clean and we read and understand our manuals and our presses.
e. One plus on the side of the 550 ...is it does have conversion kits for some older rifle calibers...if that is an issue.../ but most of us these days ...load common calibers....in rifles and handguns. But a 550 would be a good press for hunting ammo / or high caliber rifle ammo that you only want in smaller volumes.
If you want high volume (and reloading isn't about speed -its about consistency and accuracy of my rounds ) / but if you want high volume 800 - 1,000 rds an hour ...then the Dillon 650 is the way to go with a case feeder. I like reloading - but I like it more when I can crank out 20 boxes an hour....vs 15 boxes an hour....( or 4 boxes an hour on a single stage - which I did for many years too )...I've been reloading for 50+ yrs ...and for what its worth, I'd buy a Dillon 650 again ( mine is probably 10 yrs old now )..