ALL of Mxy's appearances being canon to him isn't exactly a new concept. That's why I have been arguing it for yearS. Here is a much older example of his... 'Uniqueness':
http://i.imgur.com/vKycfkFh.jpg
The recent AC issue just extensively reconfirms this fact, is all.
*As for this thread: Mxy wins, imo. Powerful as they may be, Thought-Robot and Mandrakk are still 4D entities, thus are transcended by 5th dimensional entities. Theoretically, the difference in scale between the 5th and 4th dimensions would be proportional to the difference between the 4th and 3rd dimensions -- ie. the 4th-D would be germ-esque in comparison.
Remember, though: the 5th dimension is metatextual in a sense, as it quite literally IS imagination. As such, it is beyond the multiverse all together -- that's why it wasn't listed on Morrison's Map of creation.
