Answer:
he Savannah is the largest of the hybrid cats and Maine Coon for domestic. Of the two it will be very close and some reputable breeders will argue one is larger than the other.
The Ashera is a Savannah. Unfortunately, the breeders are not willing to admit this and there are many discussion forums about this issue and Savannah breeders trying to establish the Ashera breeders are misrepresenting the Savannah breed.
Here are some posts about the Ashera cat issues being disputed: http://www.messybeast.com/asheras.htm
quoted from the website
"The "Ashera" Serval hybrid recently appeared in the media as an exotic pet with a premium price tag. The Ashera is a marketing, rather than breeding, venture and its creator is a CONVICTED FRAUDSTER with a history of leaving other people out of pocket. Both the Ashera and his previous invention, the hypoallergenic Allerca cat, fit into his pattern of persuading people to part with large amounts of money up-front for franchises and hyped products that appear too good to be true. His several pet-related schemes, though hyped in his companies' press releases, have attracted adverse media and legal attention."