The Note 8 comes with both apps and I prefer the Peel app. It has more controls so I can actually control my DVR. Can't do that with the Watch On app on my Note so far. So unless the S4 has an updated version, it seems the Peel app has more functionality.
Would like to help clear up any questions you may have. The Note 8 and future tablets remote control functionality is powered by Samsung. The GS4 RC is powered by Peel.
Both are similar. Presently Peel has multi-device control and multi-room configurations. The Samsung version will have this and a lot more in an upcoming release.