One thing i will say about these two is that sanogo will finish more often than not whilst lukaku doesn't finish quite as well but hes better for the team.
Sanogo for example gives the ball away a lot, so if you play a heavy passing game and reliant on the forward bringing others into play ( you'd be suprise how much this happens even if thats not the idea in your tactic) Every year without fail when i check stats sanogo has the worst pass completion rate of all my team, this can make a big difference against better teams.
So for me id get both if possible but before either id have babacar hes superior to both players. Now ill tell you that i play lukaku as AMR inside forward and baba as AML inside forward... just to confuse. Id pick lukaku if i could only have one cause i hate losing possession.