nachosdelux is spot on, but I'll add one thing... At peak times, it's hard to get a table at the Ren's CL. This is usually not a problem at the JW because they have so much seating in the main room, the hallway and outside.
With that said, the rooms at the Ren are nicer, IMO. As others have pointed out, too, the UGs seem to be more plentiful at the Ren. SkyTrain access is easier at the Ren, too. You don't have to walk on the dirty, broken sidewalk. I'd probably choose it over the JW. If you isolate the CL, though, the JW wins.