How accurate is a Snark tuner?
Snark doesn't publish their accuracy estimates, but an Internet search suggests +/- 1 cent; TC Electronic claims +/- 0.02 cents in its Strobe mode; Peterson says the StroboClip is accurate to within +/- 0.1 cent.
Are clip on tuners reliable?
Clip-On Tuner
These tuners can be fairly accurate, though cheaper clip-on tuners aren't as good in loud and noisy environments. This is because the neck will pick up vibrations from other instruments, like bass and drums. But for ease-of-use, it doesn't get much better.