Actually with Chiip Beta 4 there have been some reports of problems with GC backups. I haven't tested this yet but will be later tonight. Cadex appears to be on top of this though so if there are any problems with GC backups you can expect to see this resolved in the near future.
When (and if) Chiip, WiiFree, and Wiip all become truly open source (to my knowledge, only WiiFree has released source yet), the "best" solution will come down to the solution with the most active development team and community involvement.
Yes, I am aware that there are differences between a PIC and an AVR. But once you know the algorithms and methods applied to one solution, you can easily port it to another. So say Solution A releases a version with Whiz Bang Feature 5, and the Solution B dudes are on top of thier game, you would see Whiz Bang Feature 5 soon in Solution B. Meanwhile, Solution C team is drinking beer and thinking about sex. Even though they might have released code at one point, it is a bit sloppy and there aren't other folks on the scene who want to port Whiz Bang Feature 5 to solution C and maintain their own fork to compensate for the teams wandering, alcoholic ways.
So the best chip to get is the one with the most active team and the most community support. There is no clear winner right now, and there never may be. There could be many equal but different options.
How can you help? Test versions right after release and report bugs back to the team. Offer to beta test. Write documentation. Help others in the forums. Experiment for yourself. Get the source and play with it.
Pick a project now and get behind it. The one you pick *will* be the best, if you start supporting it now rather than wating for the answer to come out in the wash.