I'm also a regular AMS traveller and use a mix of KLM and EZY.
Easyjet usually win the price war hands down, if you book with enough notice. Booking at 7-10 days notice then it isn't surprising KLM offer a better price, that's the way LCC's work. EZY are usually always full so they can charge a premium for late bookings.
The one exception I have found is travelling at weekend, when KLM do seem to be a fair bit cheaper if you're willing to fly out late afternoon / evening on the Friday.