Technically, it works. And technically, it is “easy” – you don’t have to grab an embed code from Etsy and paste it in. You don’t have to really do much to make installation happen. However, Wix’s solution is still not ideal. Ideally, you’d have an app that was easy to install and fully integrated into your site. You’d have apps that don’t mess with your website analytics and don’t present accessibility issues like they do via Wix’s iFrame solution.
In the long-term, it affects your versatility, functionality, and, of course, your brand. In the short term, it can certainly add/take away a lot of headaches. That said, just like choosing a physical house or office, there is no such thing as an absolute “best” or “top” choice. There’s only the right choice relative to your goals, experience, and circumstances.