Motorized: Mounted vs On Foot ?

[MisterMark]

I see some motorized units have the option to go on foot.  When I read the manual I got the impression the advantage was that it allowed the unit to traverse certain terrain like streams and marshes that it could not pass while mounted with the trade off being that foot transport is slower overall than motorized transport.  

Aside from that, is there any other advantage or disadvantage to being on foot? 

I would think in combat terms, on foot would be more effective than still being in trucks or personnel carriers , but not sure if the game is abstracting that distinction or not.

-Mark