If you care about the price, you might prefer the Tube vs Elizabeth line. In my example of HP East hotel, you could take the Elizabeth line or Picadilly to District line for half the price. If returning on a morning and not using the Tube any more for that day, you do save ~6gbp taking the tube vs Elizabeth. That said, the newer cars on the Elizabeth line make for a more comfortable ride. There are several other threads on the best way to get into town from LHR.