Slightly different angle on this but BA have announced very late they will fly this route – when many families have already committed. So at this junture they have empty planes. Easyjet have planes that are already probably 50% plus full, so they don’t need to be cheap at this stage and the gap between pricing will most likely close very quickly.
If in a years time we were to do a similar comparison with both having had seats on the market for several months – then we can truly test pricing. Either way it is a good to see more routes for BA from Gatwick. And yes BA can be cheaper than Easyjet for flights with more extras. But Easyjet are a good airline (but do get it wrong) and the same applies to BA.