The KLM billboards are all over West Yorkshire, so it's a big push, as to costs v Jet2 you would have to go through both booking system to point of payment to get an accurate payment, Jet2 used to be nearly as bad as FR on hidden charges, but the recent moves ( required by the the CAA) have improved this somewhat, although it appears that have change the value of some other items, check out skytrax feed back for the fuss over now charging for drinks when you have pre purchased a meal on board option.
KLM would be the choice if transiting AMS onwards with KLM can you through check luggage ?
I still buy one way tickets and separate onward flights with a Dutch ISP address to avoid the the full APD on long haul flights, but it means I have to build in a delay factor or by a flex ticket which cost more than the additional APD