generally internal HDDs are much faster than external, because the way, data has to travel along is much longer for external HDDs, also the data volume is different,
so I guess recording on an internal HDD is faster, at least a bit.
hope, I was able to help you.
Thank you for reading my post. I hope you understand my "English".
I'm the German translator for some of Bandisoft's products and websites
(mostly Bandicut and Honeycam).