I've owned an 8 GB iPod touch for over a year now, and I've owned this Android phone (an HTC Wildfire S) for a couple of months and... I have to say that while I had high hopes for Android I am very very disappointed in it.
The Android has 512 MB of RAM and came out in early 2011 (or maybe late 2010), the iPod has 128 MB of RAM and came out in 2008 (a respectable amount of time in computer tech terms). I can't fathom why, but the iPod is smoother, it responds more quickly, and it practically never crashes (even though I jailbroke it). There is a notable lag when you press play or pause on the Android, almost like it's MP3 is running off some slow emulator program. And more than half the time, 3 seconds into a song after hitting play, you get a random 3 second pause of absolute silence. It's not too big a deal, but considering my iPod NEVER does this, I have to give points to the iPod.
On top of that you have desktop software support. On iTunes I can track my play-count (Android might have widgets that can do this, but I haven't found them). I can create and customize playlists on the device or the computer (with Android you can only do it on the device). You can customize the order in which songs are listen on iTunes, so I can put The Beatles under T (for "T"he), or B (for the "B"eatles). Android doesn't seem to have anything like this, on Android you can't even listen to songs in their natural album order, it always plays songs alphabetically (unless it's on shuffle). With iTunes I can also change and customize album artwork, whereas on Android you need to use these weird add-ons that flood your music folders with metadata to track all the album art. iTunes also uses this kind of metadata, but it neatly stores it in one location, keeping my source folders clear of anything but good music.
I know I'm probably coming off as an Apple fanboy here, but like I said, I WANTED Android to succeed, I didn't come in with any negative preconceptions. It just failed to deliver. All my props go to Apple, iTunes, and the well known iPod.
Addition:
Oh, and I would like to add I actually prefer the old iPod styles with physical keys (like my old iPod Nano 4th) as opposed to the more recent touch-screen style ones. With physical controls I remember I could reach into my pocket and change songs/volume by feel alone. I never even had to remove the device from my pocket, which was great if I was on a walk in hard weather like rain or snow. I find touch-screens awkward for their lack of tactile feed-back. So yeah, my number one would have to be the iPod Nano, BEFORE they gave it a touch-screen. I guess you could also go for the iPod classic... but I wouldn't since it doesn't use solid state memory capacity, it has a mini mechanical hard drive. This means you risk ruining it if you use your MP3 while running (which I do).