If anyone has any questions about the change, @MSchroeder answered alot of questions about the subject here
http://forums.elderscrollsonline.com/en/discussion/147073/riding-skill-instead-of-mount-skill/p1

Personally I kinda like the old system better, because you had to have a trade off if you wanted a really fast horse, or a horse that can ride past enemies easily. The new system pretty much takes out all decision making except which mount looks better