I've owned:
Korg DT-10
Peterson Strobe O Stomp
Boss TU-2
Boss TU-12
Planet Waves Pedal Tuner
Korg DTR2000 (Rackmount)
And various multi effects.
I have been able to directly compare the Planet Waves, Boss, Korg and Strobe O Stomp.
Firstly the worst of the bunch is the Planet Waves, whatever the specs say it is not as accurate as the Boss or Korg and the buffer in it causes some weird squeal when placed in an effects chain while muting and tuning.
Next the boss, the industry standard, great pedal, easy to see, does it's job and built like a tank. It's a good pedal and if I was in a band that only used Boss tuners I would pick one up.
The Korg DT-10 is a great tuner and more accurate than the Boss and the Planet waves, again built like a brick and looks fantastic in the new blue and black setup. I tuned with this and then the strobe o stomp and the differences were very very minimal, whereas the planet waves was way out .
The Strobe O Stomp, the best, the most accurate and the most expensive. To me I feel it's worth the money as I also like the idea of having a DI as a backup. This pedal I A/B'ed against the Rackmount DTR2000 and it is more accurate than it, which is good because it's much cheaper in that respect.
So yeah those are rough summaries, if there is anything specific you want to know just ask.
Cheers