howard,
You are a strange person indeed then. I fly to Amsterdam usually twice/month and Brussels usually three times/month - I would NEVER consider getting the train. Brussels to recall my most recent and worst experience - with Flybe (no issue with the Airline at all on this occasion) - it was a smooth 45 minute process from parking to getting through to the gate lounges. Sure there was a queue for security - but there usually is at that time in the morning. Got to Brussels in good time, 30 mins from leaving plane to clearing security at Brussels in peak time also.
Total travel time - probably around 2 1/2 - 3 hours. I'm not going to get that on a 2hr train to London + the 4-5 hour Eurostar, am I?