User blog comment:WhiteArmor/The Masked/@comment-452405-20100415052820

I wonder if any of their masks have evolved over time, while from the looks of Shinji's and Hiyori's maybe that hasn't been happening. And it definitely doesn't look like any of them have a ressurection as of yet, if it is at all possible for those except Tousen.

So what's the difference between them and Ichigo? One thing we know is Ichigo "naturally" gained his hollow the same way all hollows are formed while the others were made artificially and eventually altered by the Hogyoku while Ichigo remains free from its effect. Other then that what else differs between them?