Super Skrull, since he has more strength, and with Invisible Woman's powers he can just make Mimic's head explode. Besides, when was the last time Mimic actually fought anyone? Super Skrull has more experience in combat.
Actually, Golem, in 616, Mimic compied in entirety the powers of the original five X-Men as they were at the time.
There has been some conjecture as to Super-Skrull's strength level. Some say he has the strength of the Thing in the earlier days when K'lrt first appeared which would put him at Class 5-10. Others go with Thing's current strength. Depends on the writer.
I remember Mimic made a couple appearances around the Onslaught period, Sunspot overpowered him because Mimic had no control in his abilities (he'd start to mimic anyone he came in the proximity of and Sunspot was channeling a lot of power at the time). Then he and Blob attacked X-Force, Mimic had been given greater control of his powers by Onslaught, Blob got owned by Meltdown I believe, Mimic carried Blob off before the fight got worse. He's made a couple appearances since then, but nothing major.
After clearing that up...I still think Super-Skrull would take this, although Mimic does have psi-powers. Before he had powers, the Skrull was a good soldier, Mimic was just a punk.