Heaven forbid, perish the horrid thought, but say you could only have one? (Might also help some newbies in choosing)
Now I've never used a hand or "benchrest" press, so I can't comment on that, hopefully someone else can. But these are the ones I'm familiar with and likes/dislikes of each, please list yours or feel free to disagree with me!
Redding Boss single stage, if I had to, I could live with a single stage, cost effective, versatile, and very capable. But not my choice. It's just too slow!
Dillon 550B, super fast, super easy to swap over (for a progressive), very accurate and you can crank out tons of ammo with a quickness! It also has the ability (if you do) to function as a single stage, albeit rather awkwardly. If I could go back 20-30yrs and do it over, this might have been my choice, but I didn't have all the calibers I do now and I'd probably have just bought guns in calibers I was set up for. But not my choice now. It's too clumsy to try to make batches of small ammo, load development. It's very expensive to own and get going for multiple calibers, I made the statement the other day, "It seems every time I turn around, I'm sending Dillon another $100 for this or that!" Trust me, it amounts to a lot of $100 bills depending on how many calibers you want to be setup with! Using as a single stage, I'm exaggerating a bit, but I'm thinking bamboo chutes under my fingernails might be downright pleasant compared to that! It's doable, but not fun!
My choice, the Lee Classic Cast turret. It's cheap to buy, $14 for a "caliber conversion", you can use what you already own +\- a few items that are all around $30. It's not miserable to use as a single stage, it does small batches the same as large batches and while it's not ever going to hit 500rds per hr, it can crank out a decent amount of ammo a lot quicker and easier than a single stage!
So what's your choice and why it over something else?