iphone 3gs or ipod touch second generation better for games

My kids were using our old iphone 3gs phones without the sim to download and play video games. The phones got lost and I want to replace them and I noticed I could buy an ipod touch second generation for just a little bit more money. Does anyone have an idea of which would be better in terms of type and variety of games that would be compatabile? They are 7 and 10 so I don't want to buy them anything more expensive and they were pretty happy with the old phones.