Ravingdork wrote:
Transmutations and polymorph effects actually change one's form, which is why it warrants a +20 bonus. Illusions are somewhat less convincing for a variety of reasons, and only grant a +10 bonus.
At least, that's they way I understood it.
I would tend to agree, however when both types of spells are referenced in a entry I tend to seek clairification from the developers. If you all could flag this to the FAQ so we can get an official clairification that would be apperciated.