The dipsticks are accurate, but do have limitations:
1. If they ever get exposed to too much humidity, they won't work right. This means keep them tightly closed and refrigerated - only remove one strip at a time and immediately recap the vial. Still, after a year I wouldn't necessarily trust them.
2. Make sure the kit has the range and graduations you need - if you want to measure 0.5ppm phosphate, a kit with a low phosphate of 2.0ppm does you no good.
3. They do tend to be more expensive on a per-test basis than liquid tests.
72g bowfront planted, CO2, 2x - T5HO, Eheim 2213 and 2217, restarting after a move.
2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.