This product is very slightly better than that one

[Sutemi]

How do you indicate a very small difference in quality? I mean a very, very small difference with a strong emphasis. I don't think this sentence is quite natural:
"This product is very slightly better than that one."

 

[Copyright]

How small do you want to go?

This butter is infinitesimally better than that butter.

 

[Glasguensis]

I don't think this sentence is quite natural:
"This product is very slightly better than that one."

I find it entirely natural.

 

[veggie21]

"This product is very slightly better than that one." is fine.
or
"This product is (ever so) slightly better than that one."
"This product is just slightly better than that one."
"This product beats that one, just!"
"This product has the edge over that one."

 

[veggie21]

This butter is infinitesimally better than that butter.

Personnally, I wouldn't say this.

 

[Englishmypassion]

I didn't know the word "Infinitesimally", and its meaning makes me think why I didn't come across such a useful word before! Thanks a lot, Copyright.