Recently booked and stayed a night each in the 3 KUL based Hilton chain of hotels.
DT KL
Booked Guestroom via redemption. Received Deluxe Suite. Very impressed with the breakfast on Level 11 - was a combination of 2 restaurants with a very wide selection of local and western options (biggest selection compared to all 3 hotels). Easy to get to from KLIA train, hop on the red train line to Ampang Park and follow the signs. Exec lounge's food selection was really good too. Based on the welcome letter, they will upgrade Diamond members to Deluxe Suite on availability!
Overall, best value amongst the 3 hotels IMHO.
Hilton PJ
Booked King Guestroom, received Exec Room Plus. I checked in at the Exec Lounge just before 8pm and the staff insisted on waiting for me to take the food and drinks before they clear them away which was a really caring and thoughtful gesture. Wide variety of canapes and warm food selections for both evening coughtails and breakfast. Had made to order eggs at the lounge as well. Was pleasantly surprised at the overall quality and service. Also, it's a mere RM$15 by taxi straight from the KLIA train. As it's the cheapest Hilton hotel in KL, it's definitely worth considering.
Hilton KL
Booked King Deluxe, received King Exec Plus corner room (or I think that's what it was, based on the floor plan, it was certainly the larger room on the exec floor). Basically I was allowed to stay as long as I like at the exec lounge after the extended 3pm checkout. If you want to, you could practically live on exec lounge's food as there's even tea (with scones, finger sandwiches and cupcakes) served at 3pm. Great service overall.