Have owned a 2006 GS 430,which is rear wheel drive, and am now driving a 2015 LS460 AWD . Two entirely different cars. The GS is sporty, responsive, and has a decent ride. The LS is a true luxury ride with good power, more space, especially for a rear seat passengers, and decent handling.
The GS is way more fun for aggessive driving, the LS is the better long distance touring machine. As far as ownership costs, I have seen zero difference, the GS was bullet proof to 180,000 klms, and the LS has been too, but it only has 90,000 klms so far. I can't honestly say that repair costs have ever been a factor on any Lexus or Toyota product I have ever owned, and I have had many.