You could compare raw FLOPS (Floating point operations per second) but that would only tell part of the story. These supercomputers are highly engineered for low network latency between nodes, which is necessary for many scientific workloads. Google and other companies are generally able to express their algorithms in highly parallel ways, which means there are much reduced requirements for communication between nodes.

Therefore, even if the raw performance in terms of FLOPS sound similar, the two systems will have widely differing performance on real workloads.