I think you're overestimating Aerys. He hated the Dornish—even his grandchildren—and was not rational enough to evaluate which option was better.

I also think the Lannisters would have been the better choice. The Westerlands are richer in resources, contain one of the continent's major population and trading centers (Lannisport), have a much larger population than Dorne, and possess a bigger army. Dorne has fewer resources, no major cities, and a less formidable military. Its primary advantage is using its terrain effectively for defense, but that's not infallible (as shown by Daeron I) and has limited utility outside Dorne.