Microsoft recommendation is keeping the same url, right? if we use different URL, what's the potential risks? thanks.
You can use same url or change the URL at the destination farm.
If you use the old url, only thing it will take time when you point your DNS to new servers.
If you use new url:
- People who bookmarked the old url will see the difficulites
- if some site collections hardcoded url they will upset
- or if you have custom app which use the hardcoded url then they will see the issue.
- you have to update the mysite host url
But all these issue are fixable, as clients needs to update their stuff. But i am telling you it is painfull, when 100s complaining about it.