Actually the Eurostar is pretty comfortable in 1st and 2nd class (and gets you mileage on UA too).

The main difference is that in 1st you get a meal service whereas in 2nd class you have to go to the bar. They also have a trolley service in 2nd class.

Seats are confortable in both class (and I'm 6'4) and 1st class gives you lounge access (useless).

Please come to Paris so Blair and I can get into a contest of who knows the best place for Pain au Chocolat in Paris .