I am looking at UC returns to DXB and it's coming in around £1500 cash or £1300 M+M.
I remember from a while ago that M+M isn't supposed to earn miles but that you still can earn miles and tier points if you file a missing miles claim .... is that still the case?
Depends what your long term use of your miles in the future and how fast you again new miles. If 15k is easy replaced and you've got no immediate plans then possibly I'd use them. I recently got my miles and tier point from a m&m flight plus bonus miles and tier points as a promotion was on.
The cheapest way to buy miles is via miles booster where 15K miles would cost £150 For those miles they will reduce your fare by £200. Seems to me you make £50 on the deal. Also, there is no guarantee on future value of miles so I'd spend them.
I was in a similar situation. I ended paying £1300 UC return to NYC for New years Eve as opposed to £900 and miles. I figured paying for the flight in full would not only earn me 10000 miles (roughly) but it would also give me 10 tier points which will allow me to move up to silver status. Figures quoted are an estimate.