Sorry, I'm going to have to argue the other side, for "equal time".
The 550b can be used to do one thing at a time, not a whole lot different than a turret press. It takes 4 pulls of the handle to run a case through, but you get to see and adjust each step as you go, without fear of multiple stuff happening all at once.
I did it that way, quite a few years ago.
Once you get it all adjusted and you believe it is consistent, you can step up the pace to progressive operation.
And, if it just doesn't feel right, step back to running it like a turret until you figure it all out.
I have read quite a few posts of folks who got themselves into trouble with a single stage. Double charges, squibs, incorrect seating depth, incorrect crimp, and whatever else can be done wrong.
IMO, a single stage press is no guarantee of safety. About all it will help you do is figure out you have made a mistake after 50 rds instead of 500.
The progressive vs. single stage press decision is correctly based on two things -
1. How much do I shoot? 2000 rds/month or 200 rds/month. Do I have time to do this on a single stage press?
2. Can I afford the additional cost of a progressive press?
It can be really, really tiring (and perhaps error-prone) for the guy with the single stage trying to rush his process and get 2000 rds loaded. He is a candidate for a progressive.
On the other hand, the guy who buys a progressive who doesn't load enough to justify one hasn't hurt himself, except financially.
Regardless of the equipment chosen, the individual has to understand proper reloading practice to reload safely...
.30-06 Springfield: 100 yrs + and still going strong