ok so on way to work this morning slipped on some ice and original iphone screen is now spidered

Now do I go with a cheap 50 dollar upgrade to Iphone 3gs or pay the 170 for iphone 4? I was really hoping for it to last till iphone 5 but I guess I could always just try and sell my new one in July for 400 and upgrade again assuming apple/rogers keep the same pricing