I think Falcao may have been the better goalscorer. But he is coming off a lengthy ACL injury so who knows? Essien was never the same after his. Personally I feel that Costa is someone who improves the team as a whole, kind of like Mandzukic at Bayern. Gomez was the better goalscorer imo but it was with Mandzukic that they were a real powerhouse. Similarly, Falcao was great winning the EL and Copa Del Rey, but it was with Costa that Atletico managed to break the duopoly and win La Liga almost the CL. Still, I do hope that even if Falcao scores loads, I hope that MU won't get a CL spot so that they have some financial problems to contend with. As it stands MU have insane money to spend with their brand name and sponsorship deals.