They have some experimental features enabled there which they don't in other channels.

For example, I'm running Nightly, and the Dev Tools>What's New tab says the "Debug Variables with Watchpoints" (break when a property is read/written) feature is in Developer Edition (and presumably not in Nightly or the Release channel).

It is somewhat newer than mainstream, does not require to enter "yes I'm sure" when opening the dev console and has actually a beta qualifier as version number. I haven't run into any stability issues though.