I'd say, based on word of mouth around here, it's overall quality and the difficulty of finding one these days, the Darth Maul 1:1 bust is the grail of Sideshow's entire SW offering, that or the Grievous Ex. PF.
Does grail mean the highest price you have to pay when you buy it? or highest ratio of market to original retail? or simply the one you think is the "best"?