The contradiction lies in a naming confusion: I was talking about plain downloaders that don'n alter the material. Not about downloaders that convert in the same process. With Youtube and other streaming sources you're best off to keep the material in it's "original" format like .flv for Flash-types .rmvb for Real-Media types etc.
If you must convert though, you'd rather go for a smaller screen size (like converts for cell phones) that way you keep distortions and blocks to a minimum)
Since Youtube clips are usually offered in different qualities, you want to make sure you always get the best possible(mostly .mp4) There are helpers out there that can grab those unaltered right off the page. Just check in the plugin/extension section for chrome or Firefox
If you get
this player, you don't need to convert anything, they all play just fine
@3D Jed: It's the uploaders who get those notifications, so no need to worry about it.
-DG