Hi Alan,
To sum it up I have found that, for example a typical 1750kg MPV will give better stability, fuel economy and space than a 1750kg 4x4 but not the traction. (though this statement is based on comparing a 2000kg+ Discovery to much lighter and more stable MPV's)
ie cruising down a motorway or to be confronted with an emergency swerve, I would be happy to tow a 1700kg van with our 1750kg S-max rather than a 1750kg 4x4 BUT come an awkward junction or a muddy field and traction could be a problem with that weight of van.
Although I prefer the stability and roadholding of MPV's I'm sure the best 4x4 is more stable than the worst MPV, I guess it's a question of "how stable is stable enough?" For me, this would be negligible buffeting by HGV's and no sign of snaking up to 60mph WITHOUT the use of a stabiliser.
If you are happy with the fuel consumption of the sorrie then it sounds like it does the job for you
What MPV would I suggest?
We ruled out the Sedona without a test drive on fuel consumption and style, other posters have also described it's handling as "Lollopy" which is not for us.
The voyager was ruled out for similar reasons to the Sedona as well as reliability and safety.
Another Sharan (or Alhambra) was considered but ruled out as ours had poor reliability and the lift out seats were a pain.
The Espace was ruled out due to poor reliability reports, syle and fuel consumption figures as well as lift out seats.
Zafiras, Tourans, Cmaxs, Picasso's were all too small
The Toyota Previa Diesel is gutless
The new Galaxy was more expensive than the S-max and reminds me a of a hearse.
We chose the S-max as it drives like a 7 seat hot hatch, it looks more like a hatchback on steroids than an MPV but there's a lot more space inside than the outside looks suggest and the fold down seats are much more convenient and it costs us at least