Chunneling vs Flying from London to Amsterdam
 

Anybody knows which one is preferable?

You may be able to do it more cheaply (and faster) by flying. We've taken the Chunnel from London to Paris (back in 2002), and the Thalys from Paris to Amsterdam (a couple weeks ago) and enjoyed both experiences very much. It took about 2 1/2 hours to go from Paris to Amsterdam. The chunnel from London to Paris was longer. Even with taking time getting to and from the airports, I suspect it would take less time for a flight (with the trip from London to Gatwick or Heathrow or whichever being the longest...there is a tram you can take for 4Euro from Schipol to downtown Amsterdam that only takes about 20 min).

Flying is quicker and probably nearly as cheap if not cheaper.
Train to Amsterdam from London is not that straightforward.

So you're saying the 2 hour flight (Easyjet/BA) plus 1-2 hour pre-boarding and double airport commutes are still faster than the chunnel plus the Brussels-Amsterdam train.

London and Amsterdam are in different time zones. For real duration of flights (and train travel) you have to subtract one hour from the given arrival times on the Continent. SO your "2 hour flight" should last in real time just 1 hour.

The Eurostar/Thalys combination via Brussels can be as fast as 4 3/4 hours to 5 3/4 hours. Which is more or less on par with what you will need city center to city center by air.

There is no rule if train or flight will be cheaper. You will have to check the days you wish to travel to see if you can get discounted train or air fares, respectively. For a full insight on prices you will have to add costs to get to/from airport or to St Pancras station.

London-Amsterdam is Europe's busiest route with regard to air travel. So flying is not the most unusual way to travel between those 2 cities. Sometimes Eurostar has no cheap tickets and budget airlies have €1 flights, so even with costs for luggage and commute, the costs to travel by air can be a fraction of train travel. But, as I said, it all depends on what prices you see for your dates, or if you were willing to pay, say, 100 GBP to go by train when you were able to go for 30 GBP (all in) by plane.

If there is no big difference in costs, I'd prefer the train. Going under the Channel adds a bit of travel experience, and changing trains at Brussels Midi station is fairly easy, also with luggage (elevators, escalators available).

They're both boring. Go to the Seat 61 site and look at the train/ferry/train option

Thanks for all your good insight!