Unfortunately, I do not know which path, statistically, gives you the better chance at becoming a Marine. Marine options scholarships have become very difficult to get both as sideloaded scholarships as a college programmer and as a transfer from NROTC. Here are three quotes from
@NavyNOLA . The third one implies that since you are competing with the sideload your chances are statistically the same. If you are OK with serving in the Navy, but would prefer to be a Marine, take the NROTC scholarship and hope for the transfer. One other point, if you desire to be a Marine Pilot, your chance of getting the transfer or a sideloaded scholarship greatly increase. It seem Marins are challenged filling pilot slots.
https://www.serviceacademyforums.com/index.php?threads/transferring-rotc-units.53998/#post-531408
"Looking at an average of the three most recent fiscal years, MCRC receives approximately 94 scholarship allocations per year, and they receive about 250 applications per year for their twice annual side load boards. Sophomores have had the highest selection rate, at about 45%. Interesting fact- of all those selected, typically about one quarter are seeking Marine Aviation...
The FY17 fall side load board was particularly brutal, though, and isn't very representative of other recent boards. They saw 136 packages and only selected 15 for scholarships. For whatever reason, authorized allocations were a lot lower than expected.
Projections for FY17 spring side load board:
Freshmen Side Load: 36
Sophomore Side Load: 12
Sophomore Advanced Standing: 12"
https://www.serviceacademyforums.com/index.php?threads/nrotc.52019/#post-512830
"To throw this out there, change of options, whether Navy to Marine or Marine to Navy, are difficult and rare. You can apply (starting after freshman year), but expect to get turned down. The Green to Blue board happens every summer, and for summer 2016:
-There were 7 Marine to Navy change of option nominations for rising sophomores- 1 was selected
-There were 3 Marine to Navy change of option nominations for rising juniors- 0 were selected*
*Of note- all three were offered the option of dropping their Marine scholarship and accepting Navy option Advance Standing
I don't have the Blue to Green numbers handy. Bottom line, don't walk into an NROTC unit thinking that you can just flip back and forth at will, because it does NOT work like that."
https://www.serviceacademyforums.co...holarship-to-marine-option.53888/#post-529982
"You can apply for a change of option starting your freshman year. Success rates can be low, so this isn't anything I'd count on. You are essentially competing with side load scholarship applicants when you apply for a change of option. You'll need to impress the MOI enough to her their endorsement for your package."