It's control versus convenience, not good SEO versus bad SEO.
Neither, on its own. Wix handles rendering, sitemaps, robots.txt and redirects for you. WordPress matches that with a plugin, then goes further.
Wix is easier to start. WordPress is easier to scale once you publish weekly.
WordPress.com starts at $4 a month billed yearly. Wix starts at about $17 a month in the US.
Leaving WordPress: export, move hosts, keep every URL. Leaving Wix: rebuild the site and 301 every old URL.
SEO basics, yearly cost and the exit cost most reviews skip.