The security and certainty that BA provides could quite well be a very attractive feature for someone who is more mature. Uprooting a family to move abroad is a costly experience and you then have the gamble of seeing if the whole family settle into where you have moved. If the other half is gainfully employed along with having the kids settled in school, then you would need fairly compelling reasons (i.e. unemployment) for moving long distance. BA would win hands down here versus EK.
If you are single with no dependants then (imo) EK is the better option - providing you can see yourself being happy in Dubai. The cost of living in Dubai versus UK has the potential to be lower in Dubai, if you are single. That along with the higher take home salary, means there is potential to have a little more financial flexibility for putting money to one side, than compared to being a single F/O at BA.