I would say the Micro. But only because it's your eight year old daughter.
[...]
Unless you want to play it occasionally, I would go with the Micro.
That's why I was leaning toward the Micro. Seems like I can't really goof this up.
The other reason to get an SP is because it's like all the other kids' Gameboys. The Micro might be strange enough that she isn't as thrilled with it.
And if you ever want to play older GB games, you can just buy a small flash card and emulate with Goomba. But your daughter probably isn't interested in that.
When she gets bored with it, you know I'll want to hack at it.

That's one reason why I didn't go with a GameCube or another console. I know I couldn't keep myself from modding it. The Gameboy, on the other hand, is very personal and she can control it 100%. It hers and I'll respect that. That's another nod towards the SP I guess.
It has a proprietary jack.
Yeah, I did some research. I guess they combined it with the AC connector. Wierd, but I guess it was required due to the form factor. Man, that thing must be tight inside.
-pmc