I pretty much agree with phorwath said and add a bit of my own opinion.
I have used Chrony models for several years. I have the remains of two of them on a shelf. The third is still in use. The problem is I loan them out and people put too much of too slow burning powder and the unburned stuff penetrates the LCDs.
A simple piece of plexiglass would solve this problem or don't loan it out.
Clouds are a problem. If all clouds no problem. If intermittent clouds then velocity variations occur. Thus it is difficult to determine which velocity to hang your hat on, cloudy or bright.
I created a large shade such that the chrono is shade at all times. And shoot only between 10 AM and 4 PM mostly to keep peace in the neighborhood.
Velocity works itself out during drop chart development (If the bullet's bc is known).
I use the chrono for ES and SD. Inasmuch as velocity is proportional to pressure the chrono helps with that also.
While the chono is a valuable tool it isn't the end all of devices.
Thus, I'd recommend the least expensive unit that will give velocity, average vel., SD and ES.