Which is the better, webm or mp4?

Are there any TRUSTED sites where you can simply enter in a url or embed and convert an online video to MP4 or WMV format? I'm trying to download a video from a site besides Youtube. A free online converter program would be nice as I have trust issues downloading questionable software.I'm trying to download from MTV, so the online converter must work with this site.

I sometimes burn a DVD myself and I usually simply tell people I do not do that or know how. Now I have two full length movie formated as mp4 and avi. I just want to know how to burn this two format movies into dvd available.I use to use nero but feel somewhat complex. So can you tell me what is the best dvd burning software under my windows 7 computer? It should be easy to operate for me.

I downloaded some video files with AVI format. but it is not compatible with iPad 4 ,so how can i convert the AVI form to MP4 ?

I have been trying to get this video done I made but the files are so big and HQ that they lag my software!
They are MP4 and they are HUGE. I have been trying to get them done for the past 2 days but haven't been able to because of the slowness it causes. So I want to downgrade the size so it will help me to create the videos easily.
I am currently using Freemake Video Converter, but that sodding bastard took 6 HOURS to convert in WMV!!!!
So I don't want to go through that again... What is the fastest and best converter? And what format should I convert from MP4

Cant seem to drag or see mp4 files

Why is the estimated file size is over four times the source?  Source MP4 is 730 MB, but the estimated once imported is close to 4 GB.

How does the software handle subtitles within the created MP4?  Since the freeware does not go very far into the movie and I have not been able to find anything in HELP, or guides, is this automatic, say, if the  movie uses subtitles in specific areas of the film but not all?

converting a video_ts file which is on a harddrive at 4.6 gb, but it converts to mp4 format at 95.5 gb.  Any help please?