I haven't stayed at either- but the JW had such a bad (paint type) smell every time I walked in there that I cancelled reservations I had there twice. It is a very large hotel with lots of noise and bustle in the the lobby area. I have stayed at both the Regent and Ritz on great rates and both are wonderful.
Don't worry too much about location - taxis are VERY cheap in KL so I would really base your decision on other things that are impt to you.