There really isn't a reasonable notion of more work done on one block.  A lower proof of work hash value doesn't mean the miner worked harder, it just happened to land on that value.  All output values have an equal probability, but the greater the network difficulty the fewer hash outputs will be accepted.  Under a vast majority of cases each block in equal length chains will be expected to have the same difficulty.

Some have suggested broadcasting lower POW block headers when found, something like 1/64th the current difficulty.  If miners switched to the chain with the most POW headers it should quickly move the network to one chain.

Any scheme that allows a malicious miner who withholds blocks to determine if their chain will be chosen over another can game the network in a way similar to what is described by this recent paper http://arxiv.org/pdf/1311.0243v1.pdf

I think deterministic block choices makes this type of attack even more problematic as it removes the need for the malicious miner to propagate their block faster than the competing block.

But I am not absolutely certain about this.  Need to think this through more.  This is can be tricky to figure out, any scheme you think of to fix one problem seems to cause another.