I'd be happy on the tube - but I'm very used to it and know what I'm doing.
If you want to go by road, a car service (such as Blackberry) is a fixed fee and their driver will meet you at the door of arrivals, With Uber, you have to drag yourself and any luggage to the designated area of the car park and find your driver, Lots of reports of big variation in Uber rates and car shortages at the moment - the two times I've used them (in central London, not airport) in the past few weeks involved very long waits before a car showed up.