I have an old Competition Electronics chrono as well. FWIW, I use it to test my match ammo before major matches. This is great because they test them at the match to make sure they meet standard with a $1,000+ dual chrono set up so I get to see what the variation is, and so far, their results match mine every time. I have a lot of faith in my old beat up chrono because of that.

What ever you choose, make sure you throw a level in with it. If the windows are off-level too much it makes the bullets read as faster than they actually are.