Nina's links are great.
True answer, depends on many factors.
But, for easy and smaller files use the WMV Standard HD profile.
That is a 1280x720 Profile and uploads a 720P video to Youtube.
Within Powerdirector you can upload Video to Youtube using the Youtube profiles.
I prefer to upload video using my own WMV profile and Youtube's Upload.
You can also upload using H.264 AVCHD profiles, but the file size is larger.
Carl312: Windows 10 64-bit 8 GB RAM,AMD Phenom II X4 965 3.4 GHz,ATI Radeon HD 5770 1GB,240GB SSD,two 1TB HDs.