Best as in most accomplished combat record?
In that case, "Das Reich" and "Wiking" both had exemplary careers and took part in epic battles from Modlin to Moscow, the Mius to Mortain, Charkow to Cherkassy. (sorry, had to use non-standard spelling of "Kharkov" to make the alliteration work out
Just a step down would be "Liebstandarte SS Adolf Hitler" and "Totenkopf." They had many great successes (and several less-than-successes) but simply not as many as the aforementioned divisions.
Another step down are "Hohenstaufen", "Frundsberg", and "Hitlerjugend" - the other SS panzer divisions were fierce fighters but were simply not around long enough to gain the elan of the classic divisions.
Not to be forgotten are the numerous panzergrenadier divisions, "Polizei", and even the SS gebirgs divisions "Nord" and "Prinz Eugen", all of whom made do with less than ideal equipment and supply to great effect.
But by and large, most Waffen-SS divisions after 17 ("Götz von Berlichen") were rarely elite and, in truth, rarely even divisions in the proper sense of the word.