Sigma
I can comment on the Sigma.
I've used various Sigmas over the past few years and currently use the 1600. It works pretty well and as far as I can tell is accurate. The buttons are easy to use. The wireless kit also works well.
For my last replacement, I looked at different brands and came back to the Sigma based on the functions you get for the price.
Only complaint, the Sigma sensor on the spoke can be a little finicky and requires occasional adjustment to keep it lined up properly. Not a major problem, but some what of a pain to make a stop just to re-align the sensor. Also the rubber mounting O'rings tend to wear over time.