Yet if the OP goes with UA and gets Status with them when cashing in their M&&M miles for UA flights they would beable to change the FFN to their UA# and get those benefits. No different then when I use my Avios to book AA and then have AA change my FFN to my LT AA Plat # and get my AA Plat benefits.

Of cause it will depend where the OP is looking to cash in their miles to but *A and not UA*G doesnt go as far with UA nowadays