If your primary concern is gas milage, I would not totally dismiss the SPI. New they were rated better than the zetec or duratec (iirc). My 03 SPI still gets 30-33 mpg.
You do have to watch out for the valve seat issue, but it is not a bad motor. Mine has run strong for nearly 10 years and 115k miles with nothing more than standard maintenance and a new alternator.
as far as seating goes - I am 6'2, and was 240, i felt like I had a bit more room in the sedan than the hatch, but that was long time ago , so I may be mistaken.
Defending the reputation of the red-headed step-child of the focus world for far too long.