The time to transfer the video from your system to YT depends, of course, on your internet connection. My connection allows a 50mb upload in about 10 seconds - yous will vary.
The main benefit of this is that you don't use your bandwidth or storage space for all your videos - you are linking to someplace elce and using theirs.
I'm not an expert with videos or editing. I imagine there might be a way to compress them some, but any time you do things like that you will deteriorate the video. That is perhaps why your video is of poor quality? A web search for "video compression" might be helpful. Other than that - videos are out of my field.