Most YouTube video gets viewed at 480p resolution or less. If you send the link by email, the ebedded screen that recepients receive in the message will be small and not even offer a button to select other screen sizes or resolutions. A clever recipient might know how to use the URL link to see the video with other settings, but many will not even bother. Besides, unless one has a very good web connection, HD streaming may be glitchy, juddery, or require lots of buffering.
If you want to upload an HD version of your work to YouTube, one approach is to export your project to an MP4 file using the 1280x720 resolution and perhaps a 6mbps bitrate. Then go to the Youtube site, log in, and use its upload feature, which should accept the MP4 virtually as-is. This is the least stressfull of the HD options for most people to view. However, 480p will be the default resolution, unless viewers select HD, and even the HD may not look as sharp as the source video in its native resolution and bitrate. On the other hand, if the video was shot in bad light or was shakey, the SD and HD versions will look pretty similar.
To export to 1080i or 1080p at high bitrate, if that was the nature of the source video, might improve playback quality on the PC, but be for naught on YT, which I don't believe ever streams at over 9mbps and most people can't stream at more than about 5mbps. The YT site is not of any help, in this regard, since it only says that "bitrate is codec dependent." which is semi-true, but does not directly say what bitrate ceilings it allows for MP4 or anything else. Just remember this: most people's connections are not lightning fast, and most will not trouble to see an HD version, or they may become annoyed and quit as soon as the streaming gags.
Content is king, as they say. Audio may be the queen. Editing is the prince. Camera shake and bad light are, on the other hand, the rogue knight and the robber baron.
* Please provide details of your PC and camera specifications to your profile. Such information always helps (even if it does not guarantee) diagnostic advice.