Maurten vs GU

Hello! I am training for the NYC marathon. I have been using the GU gels for the past few years for my runs over 5 miles. I just did a 15 mile run and felt pretty good but am worried about maintaining my fuel the rest of the way. My friend just strongly recommended the Maurten gels to me. Anyone have strong opinions about Maurten vs. GU?? Is it worth it to switch over?

Thank you!