Re: Chrono
Set your budget.
I'm nuts and have more than one so YMMV.
Magnetospeed: The easiest and coolest.
Oelher: The hardest to use but most accurate (I have)
Chrony: Inexpensive and reliable.
On any day, I prefer the Magnetospeed but pistol work requires a shoot through chronograph and the Chrony gets used there.
I never use my Oelher because a buddy brings his all the time.