For occasional use, just about any of the Chony models are fine.
One thing to understand about chronographs, it that they don't necessarily give you extremely accurate readings.
The main use for these units, is to get you in the ball park and work up consistent loads for accuracy out of a particular firearm.
You also have to understand that different lighting conditions will make a difference as well. Morning light is different from pre evening light. Bright sunlight is different from a cloudy day. Scudding rain or wind blown clouds will change readings as well.
I'm not telling you not to buy one, by all means do so. They are very useful instruments when used properly.
If you hand load, you are far better off, to load for accuracy first then check out it's velocity. The accuracy is far more important than the velocity will ever be.
If you don't handload, the chrony is a waste of money that could be better used to buy hand loading equipment or more ammunition.