Season also relevant. LCY can be hellish when winter fog arrives. That said personally I would pick BA ex LCY as the Embraer fleet is a little more comfortable than the Cityjet's planes and LCY a less irritating experience for the non-status passenger than LHR. BA will offer a drink and tiny snack. LGW is pretty grim though EI are fine in flight, with one of the better BOB offerings out there.