Besides not being transportable, a platform like Wix introduces a lot of extra code on your pages for any piece of content you add.

Search engines including Google's rate websites on amount of content vs. code per page. Lower ratio of code per content on your pages help you rate better with search engines. That's another reason to go with professional developers vs. using page builders or services like Wix.

Custom design provides an exact look vs. accommodating your site to the template you purchase.

A middle option is to purchase a high quality template and apply customization through a separate style sheet. That way you save from a completely custom development, but still can create a beautiful website with an unique style.

A combination of professional design and development can do that for you.