Agree with Sunny, primarily because this accusation is not PoS specific. It can in the very same way be argued that PoW mining favours those that are able to afford better mining rigs because their share of new coins generated is greater. Moreover, as with PoS, this income is proportional to the actual investment the party has made into the currency, whether this is buying coins or running hardware.

I guess it could be argued that PoW has more variables that are related to the actual time investment of the party - i.e. mining rigs have to be fine tuned to mine at the greatest hash rate, cards must be undervolted to save on electricity bills, etc., all of which gives the poorer man a bit of headroom to outsmart his richer neighbour and improve his overall position. But yet again, the greater the mining rig involved, the greater the payoff of the extra time investment, so you run into the same issue that PoS is accused of.

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Thanks, this is a welcome method of encouraging discussion!