Should you alter the URL after setup – subdomain problem

I originally set up my site using the URL format = https://www.example.com/subdomain – I had no experience of doing this and assumed that it wouldn’t make any difference if I used
the www version or subdomain.example.com.

Now I’ve found a problem with AJAX loads that requires that pages have the subdomain.example.com format.

I can see two ways of approaching this:

• Edit all the permalinks, about 25, and change everything to the correct format.
• Use a redirect in .htaccess, something I have no experience of.

The site is still in development so I don’t have to worry changing the url from the point of view of historic visitors.

Question: Can anyone with experience in this area offer advice on the best approach to making this change – pitfalls, problems, pros, cons???

Thanks