Depends what part of London you’re in. For me Gatwick is the faster, cheaper, easier airport. It’s also the airport with the fastest security and passport control I’ve ever been through.
I also challenge the idea that Heathrow is ever cheaper to get to than Gatwick. The Thames Link service to Gatwick is far cheaper than the Heathrow express, much faster and more pleasant than the Piccadilly line, only the Lizzie line makes Heathrow as cheap and easy to get to by train as Gatwick.
I can definitely say that Gatwick is the 100% better airport for international transfers. From that angle, the only thing Heathrow has going for it is that there are many more options. From every other aspect, Gatwick is way better and Heathrow is horrific.
I also challenge the idea that Heathrow is ever cheaper to get to than Gatwick. The Thames Link service to Gatwick is far cheaper than the Heathrow express, much faster and more pleasant than the Piccadilly line, only the Lizzie line makes Heathrow as cheap and easy to get to by train as Gatwick.