Having experienced both last weekend, John Lewis probably shaded it for me, but both disappointed me in different ways.
I was after a tv for my parents, and went to Richer Sounds first. It was busy, and after queuing for a little while, I got served. The guy was polite, but in my opinion, a little condescending, and seeing as I gave him a choice of two different tvs, I was disappointed that neither were in stock.
Next was JL. It didn't appear too busy, but I really had difficulty getting any member of staff to assist me. At one point, I stood next to a member of staff (who was deleting files from the hard drive of one of the tvs), and I waited patiently while he was busy. When he finished, he turned to me, looked me in the eye, and just as I was about to ask him for assistance, he turned away and walked off. I couldn't believe it. I then walked around the department, and eventually found someone to assist me, but even he didn't seem particularly bothered or helpful.
So overall, JL just shaded it, as they actually had the item I wanted in stock, but despite the slightly condescending tone of the sales assistant, RS service was better. I understand why RS cant carry a lot of stock instore, but this small store/cheap rent policy must lose them quite a lot of sales, it certainly lost than one anyway.