I have Gizmo on my Android phone and JRemote on the phone and also on an iPad. I prefer JRemote on iOS when using it as a remote to control playback from the MC computer. JRemote on iOS will let you view associated material (such as a PDF booklet) when playing an album. JRemote on Android does not have this fantastic feature yet.
For a while a was plugging external speakers into my phone or iPad to have "portable" audio while BBQing or exercising, for example. My inexpensive Android phone will only play mp3, but this isn't a problem as MC will transcode my FLAC files (and even my DSD files) to mp3 automatically when I play them through Gizmo or JRemote. Gizmo will buffer up to 10 tracks, which is great if your WiFi signal is weak. Out on the patio JRemote on my Android phone will play one track and then stop. Gizmo will play the whole album or playlist. JRemote on iOS seems to handle a weak WiFi signal a little better, but while my phone is always available to me, sometimes someone else is using the iPad. And when JRemote is playing through the iPad I sometimes encounter a format it tries to play but cannot. I could have reconfigured things to always transcode to mp3, but I just found it more convenient to use Gizmo and play through my Android phone in most situations.
My problem with Gizmo is that it can be difficult to find a specific track. I have a lot of Beethoven in my collection, and many different performances of the same piece. Perhaps I don't know the best way to use Gizmo, but it's a lot easier for me to find specific material using JRemote. So I bought a Chromecast Audio device. If you follow the clear setup instructions at computeraudiophile.com the CCA will appear as a zone in JRiver. Now I can use JRemote to control playback through the CCA when I'm outside on the patio, with the additional benefit that the CCA will play natively up to 96/24 - not that it makes a difference when listening through crudly Altec Lansing powered speakers, but it makes me feel better. The CCA device works very well on the patio where playback through JRemote Android did not.
So there are situations where Gizmo is the clear winner (if you're not prepared to also buy Chromecast Audio) and others where JRemote is superior. For sitting in front of the audio system or home theatre and controlling playback, my choice is JRemote on the iPad.
BTW, I bricked my iPad last week with the iOS 9.3 "update". I could revive it by reinstalling and then buying JRemote again (I've never done a backup of the iPad because I have all of one purchased app and I don't have any data I need on the iPad), but I'm choosing to wait until Apple releases some fix. If I didn't have a viable alternative to JRemote on the iPad I would not have hesitated to reinstall and repurchase JRemote, because remote control of my MC computers is essential.
If I had a Windows tablet that was capable of running JRiver I'd probably use that as my remote. From time to time when listening I'll see an album that has some obvious tagging errors. If I could fix them at the time I would, but JRemote only gives you access to the tags that already have values, and editing them is clumsy. So I wait until I'm back at my desktop computer, and by then I may have forgotten what to fix. If I had a JRiver client I'd fix the tags right away. I downloaded the Remote Desktop app for the iPad, but it's really awkward to use. However, if I really had to I could update the tags that way.
