Our daughter has applied for both the ROTC Scholarship and the MM. Her recruiter said it wouldn't hurt to apply for both, even though she can only accept one. She went to basic training between her Junior and Senior year in HS and has been drilling with her Reserve Unit while in HS. This process is not essential for the MM scholarship but it helps.
Both scholarships offer basically the same benefits, but the commitment is different. The MM scholarship requires you to be in the Reserves or National Guard. Once you graduate college you cannot go active they require you to stay in the Reserves. I believe your commitment to the Reserves/Guard is a 4/4 commitment. 4 years active reserve and 4 years ready reserves. A recruiter can help you with the scholarship process. I haven't been able to find the percentage of awards.
The ROTC Scholarship has a 3 or 4 year active commitment (depends on your scholarship) and 4/5 years in ready reserves. I believe that 30% of scholarship recipients receive a 4 year scholarship and 70% receive the three year.
While on the MM you can opt for the SMP (simultaneous membership program.) For more information:
https://www.thebalance.com/simultaneous-membership-program-rotc-4139867 . In the end, it really depends on the type of commitment you want to make.