Yes they are, there is NO technical reason for an entire group conversation to have poor image quality just because one person in it doesn't have the means or inclination to use iMessage. The actual reason they do it is to get people to apply group pressure on their friends to get an iPhone, and it works. But it is disgraceful.
No. As a person who has used several Android phones. MMS sends compressed images. And that’s what it becomes, MMS. iMessage is for customers because otherwise they have everyone’s messages on their servers.