But for 30 dollars more I can get the 8gb. Is it worth it?
If you can and don´t want to spend the money on something else, yeah. Don´t expect more FPS though...
At that point you can get the GTX 1060 6Gb version, it performs better in some games, and worse on some others. The future is uncertain regarding those 2 cards. Some people say the 480 will do better in the future, because of better Vulkan and DX12 support, others say that´s not true. For now they are both pretty similar, but the 480 has a much lower price (the 4Gb version) and Crossfire support.