I'd love to see Sonic Research do a high quality clip on, but for now I think the Peterson is the most accurate as far as headstock tuners go. I know it's much better than Snark, but it's a bit cheap and flimsy feeling just like rest of them.
I hear what you're saying.
If Sonic Research ever develop a clip-on tuner, I'll buy one immediately. It would probably still see rare use, because I prefer pedal tuners, but it'd be a nice one to have, when I need to use a clip-on.
The ST-300 and ST-300 Mini are incredible pedal tuners. They're my favorites, for nice display, dead accuracy, and speed of tracking (They're blazing fast).
For pedal tuners, aside from the two Turbo Tuners, I have a tc electronic polytune 2 Noir, a Peterson Strobostomp HD, and just picked up a Walrus Canvas Tuner.
The Sonic Research tuners smoke all the rest of them, in my opinion. The Strobostomp had some nice, fancy features, like the sweetened tunings, adjustable color display, etc. But, for me, the display, while beautiful, is not as clear as that on the Turbo Tuners - unless you're right in the sweet spot of vision, pretty much standing over the tuner, itself. For me, the display seems kind of dim, if off-axis.
I'm not crazy about clip-on tuners for several reasons. Up until recent years, they've never been all that accurate.
The one quirk that drives me the most bonkers is the battery saving feature on the tc Polytune clip.
The tuner automatically shuts off after I think about three minutes. I'm so used to have an always-on tuner
I don't want to have to repeatedly turn a tuner on just to continue using it - especially when I'm doing the stretch and tune deal with new strings. Takes me about 15-20 minutes to have new strings behaving themselves (staying in tune), after re-stringing - except with classical strings.
Those take forever to stabilize.
On my boards, I have the tuners, not in the guitar signal flow, so the tuners are always always tracking - until finally shut off.. I like that...a lot :-).
In instances where I've had to use a clip-on, I've used the tc polytune or unitune Clip.
This is the polytune. I later got a unitune, and it's just as good.
For me, the polytune feature (simultaneous tuning status of all six strings) is kind of gimmicky and really not necessary. i only ever tune strings one at a time. I don't need to see the tuning status of six strings simultaneously, ever. I know it looks cute - but..why???
This picture was taken several years ago, back when I was using it in needle mode.
In that mode, it's only accurate to within .5 cents. That's not too spectacular, by today's standards.
But, in strobe mode, the accuracy goes to within .02 cents, which is incredible. As far as I know, this beats out all other clip-on tuners, for accuracy. Maybe something newer has coma along that's more accurate? The Turbo Tuners are the only pedal tuners I know of, with that same .02 cent accuracy.
Your ear gets
spoiled, once you become accustomed that kind of accuracy.
The Peterson clip-on has a very beautiful display, but doesn't look very robust, and seems really clunky. Even if it was just as accurate as the polytune or unitune, I'm not sure how comfortable I'd feel, having it clipped onto a guitar.
Some people don't like strobe tuners because they feel the display is too finicky, never quite landing on being totally still. But, once you get used to it, it can be way more accurate, and (for me, at least) is worth the extra trouble. People argue that it takes too long to be locked-in, but I don't agree. It's an adjustment, but once you've made it, the results speak for themselves.