Touch. I have one and it is awesome. I am always on it. Just don't get 8GB. It is tiny for all the apps I have such as: Asphalt 6, Madden NFL, Fifa, NBA Elite and each one is like .5GB so right there is 2GB wasted and you lose 2GB for software like iOS 5.0
If I have to go with a Ipod, im going to get the Ipod 160 GB classic one.
That's what I have and I really think that it's a very good choice. I also have an iTouch. Really nice ipod as well and it has way more features. I've never had a Nano so I couldn't say much about it. from choosing between Nano and Touch then I have to pick Touch because of lack for info on Nano.
If i was running i would be using the shuffle so i never really have a use for a nano.
They now have the iPod Multi-Touch. It's an iPod Nano with a touch screen that's the size of a shuffle. Much better for running since it can hold more music and has a pedometer on it. I have one, and I literally got used to it in about a day or so, and I used an Nano 2nd generation before getting the new one. It works like an iPod Touch, too.