If you want to know everything you can about those loads, then you do need one.
I don't agree.
You can learn a bunch about your loads with a chrono.
You'll never, ever, ever
learn "everything you can about those loads" with a chrono. You need better & more expensive equipment to pull that off.
If you want a chrono, get a chrono.
If you think you need a chrono -- get a chrono!
If you don't believe you need a chrono... you are correct.
You don't need a chrono.
EDIT: Snuffy's got great info and examples in his post. I don't mean to discount any of what he said -- I can't argue a bit with it, because it's all valid. I'm merely trying to make the point that FOR YEARS, I've seen folks in handloading forums try to tell other folks that they "need" a chrono and they aren't serious about this without one and some even suggest that it's haphazard or dangerous to continue to handload without owning and using one, and that drives me up a wall. It's a tool, like a comparator or a concentricity gauge. It's a useful item, but it's not a must-have.