How come the GoL runtimes are only ~300 times longer than the VarLife runtimes? Is it because the metapixels can be more efficiently simulated than running the game of life rules? Or because of sparsity of cells or some-such thing?
You can simulate the metapixels singificantly faster using Hashlife by caching the results for previously seen patterns. There's a pretty interesting dr dobbs article describing the core idea [1].
This is seriously cool BTW.