Maybe JLaw had better material and is probably the more accomplished actress (at the time this is written) but Romijn is still the better Mystique in terms of appearance. She looked comparably better in blue. She was a fashion model and has the better body proportion when nude with those incredible long legs of hers. I love JLaw as an actress but in this case, Rebecca wins hands down.
She is definitely the worst part of the film. It broke my heart to see one of the sexiest female in comic getting such horrendous treatment by the actress herself and also the teams behind it (writing/costume/makeup). She cant act..partly because of the writing but her bland persona definitely didn't help. Her costume sucked and she is not blessed with a body which can rock any bad costumes. You see cosplayers with better bodies at any geek-cons. And oh the hair, the horror. That has got the be the most unflattering hair-job ever. I know its the 60's but come on... they screwed January up big time there. In my opinion, TOTAL FAIL! Wouldn't want to see her ever again. Period.
P/S: Also, no offence but she's looked way too old maybe due to reasons mentioned above.