Streaming has its positives and it has its negatives
Positives:
- it saves saves hard drive space from your computer
- you can see it at that same moment without waiting for it to completely to download (that is basically what streaming is)
- you contribute to them by ad revenue (if watching legit)
- you will most likely find all the episodes together at the same website as long as there is no copyright problems that force the videos to be taken down or the hosting and the website is still up.
negatives:
- quite inconvenient if an internet connection is not present. well duh, you can't watch it if there is no internet
- You'll need a very fast connection to get the best quality unless you can tolerate videos with degraded quality
- you'll need a good connection if you don't want to be interrupted. that usually involves you being the only one with the connection and hoping that no technical problems with the connection occur like site downtime
regarding the download vs streaming, it all comes down in your preference and convenience