In short:
KL offers...
*Free access to Worldclubs
*All fares eligible for upgrades, no restrictions based on fare-type such as on NW
*On KL you can only go down one level at a time, ie if you are Plat you will be downgraded to gold next year instead of losing it all
*KL has more European partner airlines that qualify for mileage.
You have nothing to gain by moving to NW because IT IS NOT A COMP, only an exact transfer of status and miles meaning extra hassle and no benefits. There are still 6 months to go this year and with the level requirements being dropped to 60000 miles maybe you will requalify...
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KLM PE,HHonors Diamond,SPG Plat,PC Plat,SAS Silver