Most of the cargo room behind the 3rd row comes from the recessed area where the 3rd row would fold down flat into. It comes in very handy, groceries and strollers (umbrella & single fold), but you won't fit a double(non-umbrella type) into any of them w/ the 3rd row in place. I tried, the rear hatch won't lock, and will open unexpectedly or you'll get a door open alarm.
Is there some more space? Sure like I said you'll get more storage and bells & whistles. You may even have a few more inches cu. ft. wise, but for all practicallity(sp?) for stroller and multiple kids stuff...it's just about the same in that it just won't fit in either.
I rode in a buddies Sienna yesterday and there is a little more room from the 2nd to 3rd row, but it's maybe about 6 in.'s difference. The biggest difference was the headroom in the 3rd row. However, when I'm taking my boss or know I'll have customers in the car, I've never had any complaints or have seen any problems for people under 6'2" sitting in the 3rd row. Getting out was fun...but that was another story for them.
