I switched from M&M to Eurobonus for the reason that while it was already hard for me to get FTL, with the same amount of flying (and a little optimization of flights and a little Mileage run) it was possible for me to get *G with Eurobonus, while SEN would be absolutely impossible without several mileage runs. Furthermore Eurobonus offers Lifetime Gold after ten years (which I'm going after). At that point I will probably switch back to M&M and aim for HON, but that's faaaar in the future.