I use both, I use Google XML for my sitemaps and Yoast for everything else. I'm not sure if there is any harm in having two sitemaps, but I didn't want to take the chance. I have looked and couldn't find anything in particular about having two sitemaps. But, my guess is that if you do use two different ones, one sitemap may have different URLs than another, which could result in incomplete crawling of your site (this is just conjecture, though, I really don't know). You can poke around here: http://www.sitemaps.org
I think Bing natively looks for sitemaps like this: http://www.example.com/sitemap.xml
(according to my interpretation of this page http://www.bing.com/webmaster/help/how-to-submit-sitemaps-82a15bd4)