which consumes more internet/data? downloading or streaming?

It`s +/- same amount of data. Everything really comes down to several factors:
*are you going to watch the file more than once? (If yes, downloading is the best option. If no, then streaming might be more efficient)
*does quality of the file matter? (e.g. if you download file, it will be in the quality it is, while you can adjust quality and stream it in lower resolution, therefore using less data)
*do you have a lot of free space for file storing? (If the space on you computer/phone is huge, you can surely store downloaded files on there. But if you may run out of storage, better option would be to stream.)
If quality would be same, storage doesn`t matter and you`re going to watch it only once, then downloading it to your computer vs streaming(technically just downloading it temporarily in your web cache) would take up equal amount of data. :)