Getting to Heathrow from London is faster, easier and cheaper.
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.
It’s too bad Norwegian shuttered their long haul service between Gatwick and NYC/BOS. It was affordable, comfortable and convenient, so of course it went bankrupt. Now the best options are out of Heathrow (my favorite is now British Air, as long as AA isn’t operating the flight…).