Marlin and Pantheon Files look similar—are they the same?
I couldn't find a good explanation anywhere else.
The two look similar because elementary forked Pantheon Files from Marlin in 2012 after the lead dev lost interest in the project. The dev posted in May 2013 that the two were indistinguishable apart from some text changes and the removal of settings. (The dev had other thoughts on the politics of the project.) The Marlin project was last updated a month prior (April 2013), so it's safe to say that, even with its bugs, Files has subsumed its predecessor.
Pantheon Files works on other distributions, such as Fedora, though they may not be specifically supported.