gate4lounge
You might have seen me posting on the BD/LH boards as I have a similar dilemma
I agree with zvezda about points and cash which is great but small em is broadly right about the ratios
Your 30K LH / 12K BD comparison only applies if you want to redeem domestics / Western Europe and if you fly alone
For say , London - Rome for 2 LH would be :
1 x 30000 plus 1/2 points companion fare = 45000 miles ( less if you book online ) A BD C class domestic will earn you 5K miles in M&M ( once you are FTL or SEN and get the bonus ) so 9 of your BD C domestics will do.
In DC , this trip would be 2 x 20K = 40K
To earn 40K DC miles you would need just over 13 BD C domestics
Longhaul redemption is similarly good
Plus you get free u/g vouchers every 50K and other bits and pieces. I particularly like the 2 year rule.
There's no way I'm risking my BD *G but I'm going to dump this years excess in M&M and see how I go....