Yes, they are similar but support different versioning systems. Also the collaboration style is different. While Github (and Launchpad and BitBucket and all the other DVCS hosters) focus more on active collaboration between forked projects, Google Code's primary way of collaboration is through tickets.
So none of them is per-se better than the other, but perhaps fits your project management and contribution/collaboration style better. The whole debate between centralized and decentralized code versioning systems is related to that.
