The nano has features the shuffles doesn't. Do you want/need any of these features? If so, get a nano. If not, don't get a nano. Sorry, but this isn't a question that anyone here can really help you with. It all comes down with to personal opinion.
Depends how many songs you have. The 1GB Nano can hold about 200 songs and has a screen, but costs $149US. The 1GB Shuffle can hold the same, and costs $99US. If having a screen is worth the $50 to you, then go for it. Personally, I'd go with at least the 2GB, given the better cost per gig ratio.