@93_Montero: one important thing about the headroom in cars, if they have a sunroof. This costs many centimeters resp.inches, because the box, where the sunroof-parts are inside, is mounted on the inner side of the roof.
The space in buses, trains and planes is a real wide thematic. There you can find hundred of examples and experiences.
I can point out two main rules: premium bus lines are always better than cheap ones.
Scheduled flights are much better than charter flights. The seats are depending on the Airline and the usage of the plane, not the company, who has built the plane.
The best bus (coach in US-language), I've sat in, was the overnight express from Santiago de Chile to Pucon from that company:
http://www.busesfernandez.com/
Only alcohol was forbidden - so we had to hold our Pisco-bottles under the blanket.
Very ugly und uncomfortable shall be (from an European view) the bus-tours from students and school-teenager to Lloret de Mar in Spain (I haven't done this tour). The most important thing there is: cheap as possible. So you can use the pocket money for alcohol and parties.
This is a kind of European "Spring Break", you can say.
The most uncomfortable flight I had once with
http://www.pulkovo.ru/ Worse was also
http://www.tunisair.com/publish/home.asp
Quite good and with seats with space is British Airways. Otherwise: the cutest sweardesses you shall find at Virgin Air and Singapore Airlines...
A little tip to snatch a real good seat -in the business class!- : just slack around at the check-in, let all the other passengersgo first. If the plane is full then, you can have a chance to get an upgrade (for free).