We use a Mexican grackle on one of ours, which she def goes better in than the English we previously tried.
I think it's because it sits that bit higher on the cheekbones, which she seems to prefer to the pressure below her cheekbones with an English, I guess because it removes the pressure on the fleshier part of her mouth/nose lower down.
The Mexican has rings too, rather than feeding through loops in the leather, so it's that bit more stable & doesn't slip forwards or backwards, which again she seems to prefer.
She's a tricky, fussy mare - we've experimented with a stupid variety of bits & nosebands, and she seems most settled in the Mexican (with a Sprenger KK snaffle), rather than the jaw-crossing we used to get.
Not sure how useful that'll be for you, but hope it helps!