Ignore the call centre jibes. If it shows on ANA you WILL get it booked eventually.
Here are the key things to think about:
POSITIVE v M&M:
Lower redemption rates for most awards
Substantially cheaper intra-Europe awards
One way awards available for 50% of a return (M&M charges 70%)
No penalty for booking different classes (M&M charges F both ways if you book F out, Y back)
Substantially lower status thresholds
NEGATIVE v M&M:
Earning rate can be lower on intra-European flights (and worth checking the rate on other regular routes you fly)
M&M status lasts for at least 2 years (DC is 1 year)
You cannot use your miles to pay the taxes (LH allow this on intra-Europe redemptions for 15k miles)
And, for status reasons, BD Silver card holders only get lounge access when flying BD. This is the same rule for all *A programmes, of course, but if you fly LH a lot then M&M Silver will obviously be more useful.