No way I would give up Luke for Grant! A 35 year old injury prone player who IMO has a couple of years MAX left for a 25 year old, somewhat injury prone kid with great hands, great passing, aggressive defense, good rebounder, plays with fire and motivation, has TONS of basketball smarts and TONS of upside? Big mistake boys and girls, big mistake.
They are the same size, and Hill at 4 years in was very similar in terms of raw numbers to Walton, except he scored a much higher PPG, but then he was a main scoring option for Detroit at that time and Luke is not, I think he is a better passer and Hills numbers have steadily declined partly due to limited minutes and if you look at career stats (a little skewed given Grant has been in the league much longer), Walton is the far better all around player.
This isn't an upgrade anywhere but scoring, and I don't think LA needs scoring as much as they need defensive help and better rebounding on both ends of the court.