I hardly use my DS anymore because I'm bored or have beaten all the games I have and games are too expensive to buy. On the dsi, you have the option of downloading games from the nintendo store but they are pretty expensive in comparison to games in the app store.
However, I can't get rid of my DS because when certain games come out (zelda, mario) I buy those games. I just don't take chances when it comes to games I'm not sure about like I would on the iPod.
However, if he wants a DS I say go with that...it is like half the price of an iPod. You can load music onto the DS as well if you go with DSi...
Also, I have a feeling that there might be some better deals on DSi's compared to iPod touches this holiday season.
And as someone else said...the DS's aren't nearly as fragile so it is easier to trust a kid with it.
After not buying any portable electronics for 3 years I bought the iPod touch, I have the DS Lite and the PSP 2000 so I didn't see the need to pick up the redesigned models of the systems when I already had both of them. The whole redesign thing is getting old for me, especially when its just mainly a cosmetic change and doesn't actually include features that are good enough to use or that I will use, its not enough to make me spend like $200 on something I already have. I honestly have enough long RPG's to last me a very very long time between the DS and the PSP. I don't want to sell my DS either (really I would never do that) because I am a pokemon fan and there are still 2 more games coming out that can play on the DS Lite.
If you play only Mario or only one series, you will get bored with the DS, or any console for that matter. With all consoles you have to keep either loading games onto it, or buying games for it or else you will simply be bored and it will sit and collect dust. There is a point where you finish a game too, and become bored of it, then its time to buy more games, or your console will surely sit collecting dust. The thing about the iPod is it does more than games so it doesn't sit collecting dust. The DS makes a perfect companion to the iPod touch or iPhone, if I want to play a long RPG I go for the DS or a home console, if I want a quick game I go for the iPod. Although most of the iPod games I tried I ended up playing for much longer than just a few minute session!
The biggest problem with the DS is lack of some kind of way to try games, demo's are limited and only available through the Wii console, not in stores anymore (didn't ever see anyone actually using that service besides myself). If devs on the app store can put out a demo or a lite version of a .99 game, then Nintendo should be able to give us a demo of a game that costs.. a lot more. For me I really need to try a game before I buy it, it may look good in videos and screenshots but I won't know until I try.
I also like the fact that online games on the iPod are actually active. With the DS, none of the games are active, unless you get a really popular title like Mario Kart or Pokemon. As someone who has played the DS a lot, there are a ton of games I would have loved to enjoy online with other people, but opponents were no where to be found. There is also a lot of cheating in DS games, which can really ruin things (see Animal Crossing, Mario Kart).. I don't think iPod has the cheating problem, unless I am unaware of it.
The thing I figured out about DS games is even if I buy them at rock bottom prices, play them and resell them at the highest price point I can, I am still losing money. You just can't sell them for equal to what you pay. I figure with the money I was losing on DS games, I could buy a few apps on the app store every month, and be breaking even, plus saving myself a whole lot of work, which in turn, gives me more time to play games. With the iPod I also don't have to worry about running into bootleg games, which is a big problem with DS and Game Boy advance games.