Northbound is the ONLY way to go because the highlight of the tour is KEUKENHOF GARDENS. You want to build up to it. We went the last 2 weeks of April and the flowers/colors took my wife's breath away! I produced an 11-minute Youtube video of Keukenhof. Please enjoy.
KEUKENHOF GARDENS:
https://www.youtube.com/watch?v=HXO-hiLVSdI&hd=1 Enjoy!