Having experienced both, I believe it is all in technique. If a girl enjoys what she is doing, and enjoys what it is doing for the guy, that is way more important than if there is a piercing.
I've had several different women with tongue rings and personally I could always tell, never been a fan of them regardless better without but just my opinion.
I've never noticed tongue ring or not. I even had someone with a literal split tongue like a snake. Couldn't tell even a little. And let me tell you, I am not insensitive down there. Just not really a noticeable thing. Psychologically cool though
From a female perspective on the tongue ring, not really... unless the girl is really trying hard to feature or piercing.
Strange, it never occurred to me up until now that I have a forked tongue, while my girlfriend has a pierced tongue. I'd be curious to know how many men have booked us for that reason, lol.