Problem is, if Polaris is caught behind her shield trying to withstand his blasts, she will have to pour all of her power and concentration in trying to keep the shield reinforced against his power. I seriously doubt she will be able to block him and mount a counter attack. Lorna is no Magneto. It becomes a case of who can outlast the other.
I don't know how agile Lorna is in flight. If she can dodge Scott, she should be able to take him down with a piece of metal behind the head before he can take aim again.
6/10 for Lorna because she is more maneuverable owing to her flight power.