is very good airport so you shouldn't have any problems there. It is very well designed for transfer traffic allowing smooth and convenient transfers for passengers. Also an excellent airport for planespotting!
The flights are complicated question... KL
737-900 is really an interesting option and like some wrote before those birds are quite rare. 737-800 is mediocre in KL
configuration, but 737-400 are not good at all. KLM's 737-400s are very basic, a bit shabby inside and legroom isn't good either (if compared to other major airlines). If you are lucky AMS
might be operated by -800 too, but most likely it is -400...
Service on KLM flights is friendly and F/As are helpful, BUT their service concept isn't good. On 3 hour AMS
flight you'll get only a tiny sandwich and some soft drinks + coffee/tea and that is below the standards in my opinion. No newspapers on board either...
Finnair + British Airways combination is very interesting as both operate very clean, modern and comfortable Airbusses and at least Finnair has nice LCD
drop screens in the cabin, one of the best legrooms in Europe and camera views to outside. Not sure does BA
has the same....? Anyway, both offer very good service on board so these are high class products. Finnair also just improved their catering and will offer after 5th May hot meals on board... I believe BA
has some concept.
Choosing is difficult from these options but I would take BA
/AY combination instead of KL
... B737-900 is nice, but 3hrs on B737-400 is definitely not.
Despite whatever you will decide, have a nice flights and great time here in Finland!