Well, you are comparing Acura's flagship sedan to Lexus' entry midsize sedan. The Acura has AWD and more power and more gadgets since it's their latest RL. The Lexus is FWD has less ponnies, and probably doesn't match up in technology because Lexus would redesign the ES in 2007. It would make alot more sense to look at the 07+ ES because that would have the new design, new engine and everything up to date, but those models have been dealing with ecu and transmission issues so that wouldn't be the best choice in either case.
Try comparing the LS430/LS460 or even the GS model because those are the real winners and it wouldn't even be a hard decision to make because those are just superior to anything acura offers.