DSi or DSi XL conflict. 8[

I'd personally recommend waiting a little while longer. I know you say you've waited pretty long already, but later this month we'll be learning more about the 3DS at E3. If it has all the DSi's features (especially the DSiWare library), wait for that; maybe get a used DS or DS Lite to tide you over in the meantime (I've never had any issues with the power slider, so I don't think you need to worry).

If that's not feasible, I'd say it depends on how you game. I usually play my DS at home, and when I do take it out I keep it in my backpack more often than in my pocket, so if I were to spring for a DSi, I'd go for the XL to take advantage of the better battery life and screen size (both systems' screens are larger than the DS's anyway, so there'll be resolution issues either way; from what I've heard, they aren't that bad). If, on the other hand, you carry your DS with you a lot, like Phalkon seems to, it'd probably be better to go for the smaller model.

And despite what some people say, the DSi is definitely a great system. I'm just not sure if it's great enough, given that the 3DS is coming up soon; a few months ago, I'd have recommended it, but now, I'd rather wait and see.