If you upload a video using the Blogger Post Editor's video icon, then it's stored in Google Videos - which is now retired except for the part that hosts vids uploaded thru Blogger. (This was where they were being put the last time I checked, which was a few months ago)
Many people dislike this, and prefer to upload their vids to YouTube first, and then link to the YouTube video from Blogger. This gives
- Better control over the size of the video you display in your blog / website
- Video management tools (sorely lacking in Google Videos).
- Statistics about viewers
- The chance to earn money separately from your blog if your video becomes popular
- Access to many more YoutTube features.
Now you can use Google Takeout to download a copy of the original for videos that you have uploaded to YouTube - without changing the format. This is different to YouTube's download function, which only lets you download a transformed/transcoded version (eg a .wmv I just checked was available for download from YouTube as .mp4).
This can be used if you are:
- Moving your content away from Blogger / Google
- Transferring a blog to a different Google account:
Currently there is no way to transfer ownership of a video in YouTube without changing the link to it, one option is to download the original video, upload it again using the new account and edit the original post to point to the new location.