I would have though the replacement of the lift fan with fuel had a greater effect than the lack of internal gun, which of course Dave-B lacked anyway.
In any case, surely better, i.e. cheaper, to have a common variant for H.M. Armed Forces PLC than two - in which case it has to be -B or -C.
As mentioned, redesigning the carriers as proper flat-tops increases their capability no end, whether through interoperability with our allies or purchase of additional types in the future.