What is the diference between regular buttercream and Divert Sugar? whats better for icing a cake?

I have never heard of "divert sugar." I just did a Google search on the term and was unable to find any information on this. Are you sure you have the term correct?

Anyway, there are multiple kinds of butter cream.

The typical "American" butter cream is made by combining powdered (aka confectioners or icing) sugar with either vegetable shortening or butter (or both) and flavorings (vanilla being the most typical).

Swiss Meringue Butter Cream (SMBC) and Italian Meringue Butter Cream (IMBC) are very similar, both containing a meringue of sugar and egg whites with butter and flavoring whipped into the meringue. In SMBC, the meringue is assembled by cooking the sugar and egg whites over a hot water bath and then whipping. In IMBC, the meringue is assembled by whipping the egg whites and then whipping a hot sugar syrup into the egg whites.

French Butter Cream is similar to SMBC, but is made with whole eggs.

German Butter Cream is made by whipping butter into pastry cream.

HTH!

My local cake decorating store carries it and I wanted to see if anyones ever used it. I tried goggle too and nothing came up.

Ok. Realized I spelled in wrong when I did the search. Apparently Drivert Sugar is a type of sugar where 8% of it has been inverted (splitting sucrose into glucose and fructose) and it is a very fine powder. It can be used in place of regular sugar in cakes and icing, most typically when making fondant. In short, it's not an icing in and of itself.

HTH!