I am arriving on a Friday night into LHR on AA. My flight to FLR leaves the next morning so it looks like I am doing an overnighter in London. I was wondering which you would chose the Renaissance or the Marriott.

I understand that the Marriott has much bigger rooms, but the thing I care about is which one has the best option to get from the AA Terminal to the hotel and then the next day from the hotel to catch my Alitalia flight. Do they offer free bus service from the terminals to the hotel? Also what would be the most economical way if I decide to get to the hotel to downtown London to walk around a little?

Thanks for your help!