Well when I consider what the Helix Can do, I find using the built in Tuner is just fine for me.
Its when I am in the Studio that I need my Peterson or Boss.
You can live with the built in tuner pretty well, onstage or messing around, plus you can enter offsets that might be more in line with your preferred tuning.
I doubt too many people even musicians would notice a few cents off here and there.
In the studio we have been using a Kemper Profiling system, that has a good tuner in it but as soon as someone else starts playing a particular guitar, they pretty much would still have to retune the guitar.
We all hold every note in a slightly different way, plus if the room temp changes, so does all your Tuning.
Personally I have never ever been able to keep any guitar right down to 0 cents offset for any time at all, and yes we have some really nice guitars.
Yeah in the studio everyone has got to stay real close,Guitars, Synths even drums but that's one of the reasons, we use vibrato. keeps people's ears guessing :)
I gotta agree with Charlie_WattI love my Peterson