I have uploaded two different matches of sc2 custom map. First one was done with horrible FPS, second one was much more responsive.
However, somehow, the first video has a much better visual quality. Anyone knows why? What could be the sources?

First Video: http://www.youtube.com/watch?v=50HOZNPN4No
Second Video: http://www.youtube.com/watch?v=eVgzTXB98BY

EDIT: Just saw that first one was originally a compressed AVI, and the second one is a compressed MP4.
However, before uploading to YouTube, the visual quality was just the same for both of them.

Based on my experience at work, MP4 compression usually looks better than AVI compression, but that also depends heavily on the codec used and the level of compression.

I recorded with FRAPS a 17 minutes video. Somehow, FRAPS decided it would split it into 5 different files, so I had to use VirtualDub to compress all of the files, and then CamTasia to mix parts together to make 2 parts (because of maximum video length on YouTube).
The problem from there on is that CamTasia is a SERIOUS bitch when it comes to save my stuff as something. I really can't remember how I got it to save that First Video as an AVI.

since when does a container have any effect on video quality?

just save it as a 2 pass 2-5 Mbit h.264 file in whatever container you want. Avi is easiest. mkv is best. mp4 is okay.

Youtube is a horrific disaster of a service. Camtasia is a piece of shit. Stay away from it.

Use megui to encode/merge the fraps parts (they're multiple files because of the container) and mkvmerge to split as necessary for failtube.

To anyone that have watched the Second Video, look at the new one I've uploaded: http://www.youtube.com/watch?v=T_0N03n1ivk
Much better quality.

All I had to do was to understand how to properly save the project as a MP4. ;o

Quote from payne

I recorded with FRAPS a 17 minutes video. Somehow, FRAPS decided it would split it into 5 different files,

This is normal. It's saved as a .avi, which has a maximum of 4 GB filesize. FRAPS records losslessly, so that's not an obscene number of files. I've gotten 7-8 from a 40 minute LoL game, so you're fine, especially if you used fullscreen and your screen is larger than mine.

Also, youtube links with HD quality are much appreciated. Add &hd=1 to the end of any video, and it'll try to play it in 720p if the video has HD quality.

And how to force it to start as 1080p? >:D

Is the footage 1080p? "1080p" isn't an arbitrary label, it actually means something.

I'm serious. I just wanna make sure he knows that.

It means more pixels shown per I-dunno-which-unity-to-square ?

Sort of. I just no re-read your post and thought you were asking how to make it go to 1080p, rather than auto-play at 1080p. I think 720p is the highest autoplay.

Searching on the web, I found "&fmt=37", but I also found out that these little tricks doesn't seem to work anymore on YouTube, for any resolution.
"&hd=1" work, though.