To be honest it is just as easy to download mp3s in html5 if not easier. The standard is still being worked out and there hasn't been any protection implemented in to the standard yet. html5 has been around for a very long time. It has just started to get momentum with the increase usage of smart phones. Most newer browsers are starting to support html5, but in limited ways. Even html5 is continually being fine tuned and features added to it now that it has the support of some of the bigger industry players. Unfortunately most users don't have the latest and most up to date browsers, so they will have little to no support to even view html video or music tags.

I believe I saw an answer to this in another topic on the forums on how to default to just one spec of player. I however would at least suggest you take caution in doing so, especially if you plan on having this be a public website as you will be greatly restricting your users access. If your biggest concern is preventing downloading of music, then there are many other things you could look at. Such as how your music is being streamed, how the files are being displayed in the code and playlist, using sessions, etc. Even switching the player to silverlight would prevent better security if you enabled some type of drm protection, but that would be a massive rework and would then require your users to have to have silverlight installed. Also note, that even with all these safeguards in place, the general rule is if you can hear it, you can record it. Nothing is 100% un-copyable.

I really like html5, but it still has a very long way to go before it can be used as the only video and song playback method.