I would say the main difference between HTC's 'Music' and Google's 'Play Music' is that Play Music can play music from your purchased Play Store music, whereas HTC's cannot. I personally prefer the look of Play Music, (and I buy music on the Play Store) so I only use that. As for uninstallation, unfortunately not without root. But, you can disable them. Go to Setttings > Apps and slide over to the 'All' tab and find whichever one you want to be rid of. Tap on it, and select 'Disable'. This is almost as good as uninstalling the app, as it is completely hidden and non-functional. I have used this feature for some HTC apps which I never use (Best Deals). Hope this helps!