St. Regis and Luxury Collection (some of which are branded as Sheratons, strangely...) are the highest, but there isn't a strict ordering of W, Westin, Le Meridien. I'd probably say it goes W, Le Meridien, Westin, but individual properties have a lot of variation. then Sheraton, then Element and Aloft, then Four Points. There are individual Sheratons which are worse than Four Points though.

I prefer the Westin bed to the W bed; I've probably spent >100 nights in each.