dust is cheaper to produce as the aluminium is sand blasted then annoed, where as gloss finish the aluminium has to be polished 1st before anno to get the gloss finish.
As for wear they should be both the same as its a chemical process, dust finish obviousy will have a rough surface whuch could hold dirt etc more in its pores.
White anno dosent actually exist, as its not chemicaly possible its more of a really light grey which looks kinda white.