I had occassion to peer into the cargo compartment of an '09 Jetta wagon this morning and it's actually deeper (measured from back of front seats to rear of useable space) than my '02 Passat wagon by a few inches.
I wasn't able to measure the width or height of the cargo area, but it looked comparable.
I also noticed that the rear seat backs laid flat without lifting the rear seat bottoms, although this left the backs of the front seats exposed to the cargo. The rear seat backs of my Passat don't lay flat under any circumstances.
Just as I was thinking I was being priced out of the VW line for a replacement of my old boat, maybe the Jetta wagon is the one.