I went to the Sammy website and got nowhere looking for that info. Fortunately, I took a new Sammy e6500 to the beach with us and I have the manual. Let me look...found a list of file extensions and MKV and MP4 are supported, but also found this note: "Some MKV and MP4 format discs may not play, depending on their video resolution and frame rate".
Here's that list:
That's pretty much all the manual has to say about what you're concerned with. I will say the e6500 is a much better player than the three c5500s I have. The remote (which could be a bit larger) is much better than the remotes for the c5500s.