Does anyone have any experience of the relative merits of active, noise
cancelling headphones as opposed to passive, ear canal type isolating
earphones ?

I want to get a set to use with an MP3 player on trains and planes. At
the same time I would also like to be able to use them with a radio at
motor race meetings.

My requirement is to be able to listen at sensible ( low) volumes.
Decent sound quality would be a bonus, but the main requirement is
actually be able to hear music/commentary.

My inclination is to go for something like the Shure E3 or Senheiser
equivalents. But how well will they work on a plane. I can always stick
a pair of ear defenders over the top at Le Mans etc..

How good are the active devices?

T.