I live half way between the two. Ten years ago, MME was the preference if a choice of flights available. Now, there is no contest; if I need to go to Schiphol, it's NCL. In comparison, MME terminal is a hole, staff are surly, and I just don't want the tax hassle (plus the walk in the wind and rain across the apron, etc., etc.).
Even if there was a London service now, I'd still plump for NCL (or the train) for the same reasons. What's more, the interlining choices from NCL are now so much better - SN, LH, AF, etc, so it's not just the AMS connection that is important in deciding which airport to use.