Downloads changed from MP4 to TS

[Harts52]

I've been downloading classes from a website. They were downloading in MP4 format, but they recently changed to TS. I'm only downloading for personal use, and while I'd like the quality to be the best possible, file size is an important factor because I'm storing on thumb drives. I've read that TS is newer/better but MP4 is smaller. Is that right? Are there other pros/cons?

Is the download format driven by the VSO software or the video site?

[JJ]

Downloader takes what it gets.
In this case that site has changed format.