Which tool do you think should be best to create a Sitemap.xml?

It depends on your requirement.
If you are working on Wordpress, I'll recommend Yoast's SEO plugin.
It creates a sitemap and is according to the latest standards of XML sitemap for news etc.
If you need a desktop tool Sitemap Generator from WonderWebWare.com is my best tool.
It scans the whole website and provides you with a list of URLs in all formats including XML, plain text and even broken links.
You can export external links to other sites as well.
Just be cautious when you are crawling a site.
If a website has thousands of pages, this tool can take sometime to finish.
Thanks Usman

you can use any free website to generate your site map