Oh, I don't know about that, Debi. It depends on how exhausted the OP will be after the flight, and what time of day s/he lands.
Google maps shows both routes (Malaga to Sevilla, Malaga to Jerez) to be about 2 1/2 hours.
Going to Sevilla would be an easy trip. It's all equivalent to US Interstate routes. The first part, A45 to Antequera, is mountainous, but all divided highway and very pretty. Then A92 to Sevilla is also divided highway, and more like high plains.
Jerez may be a little more difficult trip, because you need to go the southern route through the Costa del Sol, which is crowded. You would undoubtedly want to take the toll road (the local route is largely stop-and-go), which takes you away from the main sight to see, the Mediterranean. Still, it wouldn't be a bad trip.
Personally, I'd take the 2 1/2 drive and save the $400. And I'd go the northern route to Sevilla, which is a much nicer city to see anyway (one of my favorites). But that's something that the OP would need to decide.
-Bob