When I last flew with EK in 2008 I went from (and returned to) Gatwick and the aircraft was older and had less entertainment options back then (332 LGW, 77W LHR I believe) than the planes going in and out of Heathrow, that was quite a while ago though.

Saw on the EK website the other day that they're starting to fly the A380 to Gatwick from March 30th so from that point I'd imagine flying out of either of the two will be a similar experience.