Be very careful with the booking classes.
The cheapest class published for that route is L. L earns 25% (933 per segment) on M&M but 0 on MileagePlus. Interestingly, L earns 50% (1867 per segment) on A3, so if you fly a lot of L you may want to credit to A3.
You say that miles&more offers only half of the miles of united this year. That happens only for classes Q/S/V/W, and those are at least $200 more expensive than L. Are you planning on flying mostly Q/S/V/W?