I think you’d be hard pressed to say Potter is a better fit as a whole. Potter works best in its atmosphere and theming; Diagon Alley and Hogsmeade are fun places to explore; their mimicry of real villages and cities with a magical twist is a great strength that gives them a leg up when it comes to designing a land based on the property. As the story unfolds around Harry’s exploration of the Wizarding world, so too can the guest explore and uncover the details of the world around them.
Star Wars, on the other hand, is tailor made for attractions. The vast array of vehicles, ride-sized sets (an important feature for a property when working within the space limitations of a theme park) mixed with the built in ability to literally jump across a galaxy in a single attraction allows for more dynamic experiences than Potter in the sense that any person could name about ten ride concepts for Star Wars without even having to think about it.
This isn’t a knock against Potter, nor is Batuu’s general obscurity in the canon a problem. But, simply put, Potter is more difficult to translate to rides, while Star Wars is more difficult to recreate for a single land due to the fact that no film in the franchise visits less than two planets, and a solid third (if not more) of the franchise takes place aboard star cruisers in deep space.
Both benefit from the presence of strong music, characters, and spectacle, which is what makes up for the shortcomings of their franchises when it comes to park implementation. The magic benches idea for Forbidden Journey is dumb, but we get to fly with Harry and co. No one will ever get as worked up over as Batuu as Diagon Alley unless they’re actually getting worked up over being in Star Wars Land. That part sounds weird, but I get excited on Star Tours because it’s a great Star Wars attraction, whereas I get excited on Gringotts because I’m in Gringotts.
TL;DR
Both lands are good choices for a theme park because Potter lends itself well to great environments and Star Wars lends itself well to rides.