While testing my sound effects and music for my upcoming iPhone game I've noticed that the external speaker of my test device (iPod Touch) does a great job of reproducing high notes and bright sounds, but doesn't seem to do much with low sounds or ambient noise with any bass in it. On the other hand, if I use the headphones, I can hear the bass and low sounds, but the bright sounds are a little less apparent.

Do most devs mix sounds favoring the speaker's sound qualities or do you favor the headphones? On one hand I can picture most gamers using the external speaker, playing it as a portable gaming device. On the other hand, it is an iPod, so if they're listening to their playlist while they play the game, maybe they've got their headphones on.

Ultimately I'll try to find a compromise that makes for a decent experience either way, but I'm wondering if others have favored one or the other, and why?

That makes sense. As long as there's a general expectation that headphones are the better audio experience, then the speaker doesn't have to deliver fantastic sound. I just wasn't sure how prevalent that expectation was.