I find the so-called ‘sweeteners’ of the Peterson tuners pretty useless - I’ve tried the ‘ACU’ sweetener (a.k.a. the ‘James Taylor’ tuning) on my guitars, and it sounded out of tune, likewise I tried the ‘mandolin’ sweetener on my Fylde mandolin, and it was pretty ‘sour’. I gave up on their ‘sweeteners’ and just used the ‘EQU’ (Equal Temperament) setting, which sounds the most in tune of the lot.

Re: tuning by ear…I frequently tune by ear at home - I’ve been doing it since 1961, so I’ve had a fair bit of practice! ;-) But that’s really not practical for gigs, sessions, clubs in pubs, etc., and I prefer the TCE PolyTune/Unitune over the Petersons because they’re simpler, more stable, and have a better, brighter display.

But we all have our own preferences, and all are perfectly valid - my ears and eyes aren’t your ears and eyes, and it’s quite rightly a case of ‘whatever floats yer boat’.