Here's a short bit about the differences between Aang and Zuko, through Katara's eyes. Well... if I owned ATLA this is how she would see them. But I don't... *sigh*

The way the water moves across my skin, cool and feather light, is nothing like his touch; Scalding. The water is more like the winds that always seem to accompany him. The avatar. Safe and innocent, kind and gentle. Like those winds. Infuriatingly like those winds. Playful and…and almost vapid. How can someone so wise know so little of how people actually work? I suppose i forget how young he is. It's easy to forget when he's leading seiges against an entire empire.
The Day of Black Sun brings other thoughts to my mind. The kiss. The touch of his lips was... like the water. Familiar. Familiar and normal, and... so very far from the prince's. When he touches me it burns, burns to the very tips of my toes. It melts me. I shouldn't care for him this way, I know that. But it's hard to help. He's everything Aang is, both parts serious and compassionate. Just like airbender. So shouldn't it be easy just to choose the younger boy? If they are so similiar why am i only compelled to Zuko. The feelings he brings. A cool shiver always seems to run down my spine, course through my body whenever his skin brushes mine. And I'm not entirely sure if it's from his fire or my water or some wonderful combination of the two. But when those sparring battles end, when we no longer have some flimsy excuse for our hands to meet and our legs to brush, that's when I see the steam. Rising up in thin, white tendrils, dancing in the air. Such winding vapors created by only us, mingling in the air above us. Playing in the other boy's element, some cruel joke. A sign spelled out clearly in space around us. Spelling out just how easily I melt when my skin touches his, when water succumbs to fire's unquenchable thirst. And all my confusion, my fight, my resistance just... Evaporates.

Hope it wasn't too confusing. If you liked this you know what you should do? Review! It's what Uncle Iroh would do, and we all know how wise he is. :D