GIVAT,
One thing to remember about Abuja is that Boko Haram detonated a car bomb at the UN Headquarters there in August of last year which killed at least 21 and injured more than 60 people. The Christmas Day bombings by Boko Haram which killed at least 25 were in Madala on the outskirts of Abuja. Abuja is undoubtedly nicer and has a kinder climate for an expatriate, but for the last year it has been in US embassy warnings of the possibility of suicide bombings in hotels.
Lagos is bigger, dirtier, busier, floods in the rainy season, has terrible traffic jams and, like any big city, has all the usual problems of petty crime (though armed robberies have definitely reduced in the last 5 years).