The OP doesn't say, but the earning rules of the FF scheme to which the miles might be credited might be relevant. Mine doubles the mileage for travel in C (from 600 to 1200 each way), so for me the small extra cost - especially when compared to the price of short haul flghts in many other parts of the world - is certainly worth it. I get a better seat, a better snack/meal, lounge access at Phuket (though I should have got that anyway) plus 1200 extra miles.