Thanks for sharing your video.
If you want, you can also manually change the size at which your footage is recorded. For this, you need to go to:
Computer>Local Disk>Program files>Electronic Arts>The Sims 3>Game>Bin>Sims3
If you have a stuff pack or expansion pack installed, you need to alter this file in the directory of the newest game instead. If you have the Sims 3 + World Adventures, for example, instead of going to the 'The Sims 3' directory you go to the 'The Sims 3 World Adventures' directory. If you have the basegame + WA + Supernatural, you need to go to the 'The Sims 3 Supernatural' directory.
This ini file (Sims3, which you can open with Notepad, for example) contains the recording properties, which are on top of the list.
Let's assume you want to increase the recording size, so you'd get HD images on youtube. For this you'll edit the numbers behind ''Large'' to 1280x720. When done, you simply save the file.
Make sure that you have the recording size in-game set to large, or whatever value you edited the numbers for (And also keep in mind that increasing these values will make filming more demanding on your computer).
It doesn't matter what resolution your game is set to, because the recorded footage will automatically be converted to the assigned resolution.