Lived in Spain last 15 years. Have never stopped but have driven through Seville a few times on way to Portugal.
Imagine serious London rush hour traffic on speed. Bus services are ok, so if you can go Malaga to Seville easily, great but you expose yourself to buying the right tickets, finding the bus in what will be a busy station, finding your Hotel from Seville's bus station etc. You may not be saving money.
Personally, I'd fly direct to Seville, find Taxi rank and tell them your Hotel.
Word of warning. I've bought tickets for Spanish buses on internet from official site only to find others in my seats when getting on and the seats sold twice over. And trust me, you will be wrong and they will be right.