I came from PC to Mac and was disappointed with JRiver. On Windows this media player has everything you will ever need for playing all kinds of multimedia files. It's very fast and works without issues. Organizes and analyzes all your audio, video and even images. As everyone already noticed, development of Windows version is very fast and is constantly being updated with bug fixes and new features.
The Mac version is another story. On my 2014 Mac mini JRiver was incredibly slow, interface didn't work as expected, there were major video issues with files that worked flawlessly on my previous Windows computer and many little things that bothered me, such as lack of certain keyboard shortcuts. But what really prevented me from throwing another spicy amount of $ to JRiver, Inc. bank account was audio playback. Some files didn't play, others had to be downsampled for some weird reason, and some frequently crashed the entire application. God forbid you play some multichannel content on a Mac. It was a complete disaster, as if it wasn't being made by the same people. Complete contrast from what I learned to love on my PC and honestly, the only thing I really miss from PC on my Mac.
For now, iTunes will suffice, but until they start some serious development for Mac version of JRiver they are certainly not getting my money, and they shouldn't be getting yours either. Try the trial version and see if it works for you. You've been warned.