This thread isn't new but should help (and be enough to put you off the CP Kensington). A bit of searching should get you to several other threads comparing London properties. It's fairly easy to identify the posters who know what they're talking about (answers from Raffles are typically among the most useful).

I've booked the HI Mayfair for my next trip because it's much cheaper (for cash) than the IC for my dates. Lots of "basic needs" stuff within a couple of minutes' walk (Pret for coffee/breakfast, M&S for wine, Starbucks if you really must). But it certainly isn't hip or cool, and if I was using points I'd spend a few extra for the IC. (I don't think I could ever be happy parting with 35,000 points for a Holiday Inn when there's an IC just down the road for 50,000...)