As with most questions, it depends.

If you're riding across the Great Plains, no trees, buildings, or mountains in sight, and very few curves, a GPS (either stand-alone or on your phone) is probably the most accurate.

After careful calibration, my wired computers are within 0.5% of the distance shown by a GPS on an open course, or surveyed mile markers. (Note that Kansas and Missouri, at least, have road markers with little or no relation to distance.) I know a couple of beautiful rides where the mountains, curves, and trees interfere with GPS signals, and so the wired computer is (by far) the most accurate.

Wireless is similar to wired, except where it ain't. Near some power lines, neon signs, and high power headlights are some of those "ain't" places.