Price Comparison Sites to be investigated by the CMA

Legacy_user

It would seem that the CMA's investigation in to the domestic energy market isn't complete. Comparison sites have been included in the CMA's 2016/7 work plan.

http://www.out-law.com/en/articles/2015/december/price-comparison-sites-to-be-scrutinised-by-cma/

Consumerist

I heard on BBC Radio 4's Moneybox program today that the CMA is proposing that only Citizens Advice will offer a true all-of-market comparison site.

Presumably, the other sites will become known as energy advertising sites who will be able to do deals with suppliers and charge them what they like in advertising fees.

In principle, this sounds as though it could be a good idea. We, the customers, can completely ignore the advertising sites and just go to the one true comparison site for tariff information. It is proposed that Citizens Advice will not be able to initiate a switch in the way the advertising sites will be able to.

Is there a down-side for customers I have missed?

Edit
Will switching through these advertising sites be any cheaper than going direct to the supplier? Will these advertising sites even be needed?