AFAIK, the Mobi format doesn't do SVG (KF8 does, but I hear it's not that good). There may be other technical issues, but otherwise they're pretty much the same thing. I'd say about 98-99% the same thing.
Amazon is being a little b***h about supporting ePub (considered to be the standard in the publishing industry) and wants you in their ecosystem, just like Apple; a closed off ecosystem (or a "walled garden"), where only they control what content you may have on the device that you purchased. For this reason I'm never buying a Kindle, and also not another Apple product ever again.