Graphtech Tusq Nuts

[The59Sound]

Quick question that is not clear online: 

What do the Tusq XL nuts have that the non XL version doesn't? 

Which one is best? 

[Lozz196]

I’m just having one - the XL - installed on a Precision to match another which already has one. I find that the tuning is smoother with the XL than with the stock Fender nut, no experience of the non-XL Graph Tech tho.