The simple answer is Heathrow. It's approx 22 km (12 miles) west; Gatwick is approx 47.5 km (29.5 miles) south of central London. Both have excellent transport connections. However, the most convenient will depend both on which terminal you arrive at, and where you're staying in London; Central London covers a huge area.
The Heathrow Express train to Paddington cost £20 when I took it a week ago. 15 minutes from Terminals 1-3 station, 20 minutes from Terminal 5, longer from Terminal 4 because you need to get a shuttle to the Terminal 1-3 station. Great if staying near Paddington. If not, you'll have to take the Underground, bus or cab to get to your accommodation.
The Underground is considerably cheaper, but cost depends on whether you're using an Oyster card, Travelcard or paying cash. The journey is much longer (about 50 mins), because it stops at every station. However, if your accommodation is near one of the Piccadilly line Underground stations, it could be more convenient.
Gatwick airport to London Bridge with First Capital Connect costs £10 and takes 28 minutes. Gatwick to Victoria will take 30-35 minutes and cost from £14.40 to £19.90, depending on the train company chosen. Same issue as for Paddington. If you're not staying near London Bridge or Victoria, you'll have to take the Underground, bus or cab to get to your accommodation. over 6 years agoAnswered by John via Travellr.com
I arrived at Gatwick recently to find that the airport express train cost something stupid like 30 odd pounds. The regular all stops train was a bit cheaper, but still a stupid price.
Bottom line - both are just as easy to get to as the other really. Just that Gatwick is more expensive, and Heathrow is slightly quicker. about 6 years ago