Generally, creating your own tables is discouraged. Back in the day, it was common to see plugins create tables. In a lot of ways, plugin authors didn’t have much choice, but it did make a mess especially because it was common for plugins not to clean up after themselves. I get that, and agree that publicly released themes and plugins should not create tables if it can be avoided.
Having said that, I would lean towards creating the tables. I’ve done something much like what you describe and maintaining and improving that subsystem is still a big part of my job. I have considered post types but can’t convince myself that they would really work for the business listings, though I am using them for a ‘business bio’ component. The relationships I need, the searches, the performance… I just don’t think it would work if I hadn’t built my own tables.
Yes, you have to build your own interface but the “post”-like interface makes no sense for the data anyway, at least not for mine.