I flew with KLM intra-Europe uncountable amount of times. I would go for the emergency exit seat on all plane types, except for 737-700. The reason being, the seat in front is missing, thus one doesn't have a seat pocket to put anything in and you need to ask two people to move when you want to get out to get something from the overhead bin.

PS! On all the Boeing 737 flights, economy comfort comes with an electrical plug. Very useful when you need to work and know that you will not have a plug for a while after the flight

SB