Bentley hands down. The location is a bit quieter but you are close to the V&A, NatHistory Museum etc. and also an easy walk to the peace and serenity of Hyde Park. Take the tube, a bus , or a short cab if you want the fury of regent street. Finally, the Bentley, well it just makes you feel more like you are in London. I stayed there a couple times multi-day before moving to London - where I now reside