Q: The rise in stock prices of a few mega-caps (Apple, Facebook, Amazon, etc.) has distorted the concept of broad diversification through index investing (S&P 500). While the index rises, many index constituents have performed poorly.

Some ETF providers have created funds that hold a subset of the components of existing indices. Inclusion is based on their concept of company "quality". Presumably this eliminates poor performers and results in a "better" fund.
Examples are: ZUQ, SPHQ, QUAL, ZGQ, ZEQ.

Please comment on this idea of "quality" subsets of existing indexes. Do you consider this to be a useful investing strategy? Would you consider the examples listed to be preferable investments compared to the broader indices?

Thank you.
IslandJohn