said by Pringlescan:watchespn.com too is the same as ESPN3. Look at both of them and they are the exact same.
Espn3 is also known as espn.go.com. Which is the same for watchespn.com.
As for connecting from a different ISP, that's why it's a mediacom exclusive. If it wasn't it would be allowed connection from anyone.
They are very similar but not the same thing, and it can be confusing to describe the difference, especially since ESPN made some changes with this a year or so ago.
WatchESPN is basically the platform to watch any espn content online.
However, unless your provider is full watchespn provider, you can only access a subset of what's on there, the content that's ESPN3 only. Everything else, such as stuff that also runs on ESPN1\2\U, your ISP needs to be a full watchespn member.
It
used to be that almost everything from ESPN1\2 was also available on ESPN3, but theyve moved away from that, probably because it was a great way to cord-cut.