About a 50/50 if I take a MP3 player with me, but when I do here's what I take and my thought process. I found a cheap Chinese MP3 player that runs on a single AA battery. It has a very limited display. (like a wristwatch.) One battery will usually last a whole trip depending on length of trip and how much I actually use it.
Now, here are the reasons I use it.
1. Occasionally I just have to "crank out" some miles. I don't like to hike like this, but occasionally the goals demand it. For this I load Cadence drill instructor stuff. (Hard core ;D)
2. When I'm going to be out on the trail on a Sunday I'll load a sermon and some church music. For the time that service is going on back home I have church out in the woods. Very refreshing change of pace! (If I'm reasonably certain I'm alone I'll even sing along. )
3. General use. I often hike alone as such I occasionally have the need for "human contact". This loneliness doesn't often hit, but when it does, general music usually does the trick.
Love that my MP3 player is NOT power hungry and that it uses the same battery that other gadgets that I carry use. Also, I've never lost or broken it, but if/when it happens I'll grab another one off Ebay for $10 bucks.