If you're arriving London late in the day & just doing a hotel overnight stay, the Paddington is the best bet as it is directly adjacent to Paddington Station and the Heathrow Express to LHR ( HEX is a bit pricy, but well worth the convenience of a 15 minute ride to LHR as opposed to what the Underground offers as a 45 to 60 minute journey depending upon from where you leave ).

Even if you make it a day in London, Hilton Paddington is still a very good location as you are all of a 12 to 15 minute walk to Marble Arch Underground Station or walking along Oxford St to where ever you want to visit ( We ourselves stay at Marriott Marble Arch which is some 5 blocks south of Hliton Paddington and we arrive/depart LHR via Paddington and walk all over London from here ).

Have a nice holiday stay