I've had both.
Hi there,
I have had both vehicles, now being the current owner of a 2012 ST D40.
My D22 was a 2010 model, stock standard except for tub liner and tonneau cover.
The D22 was a good value for money car costing me $31k drive away, however I found the ride rubbish, it would bounce all over the rd. The bluetooth reception was crap, the vehicle had a knocking noise under my foot whenever I turned left hand corners. The rear seats were small and the vehicle did not come with an anchor for a baby seat, which I knew when I purchased it however my circumstances changed. Fuel economy wasn't bad however not exceptional either. Apart from the above mentioned items the vehicle was as I expected from a brand new $31K dual cab 4x4.
The new D40 is like comparing apples and oranges and these vehicle really are not comparable. I picked up this vehicle for $39,500 drive away with tonneau cover, tub liner and tow bar. I have only travelled 3000km so far but I have been more than impressed with the the power and fuel economy averaging about 8.8 l/per 100km. There are a lot more creature comforts as well which is to be expected with a vehicle $8500 dearer. So far I have only done some really minor off road work and I have noticed that the vehicle suffers from low clearance, also the tyres which come with the vehicle are crappy road tyres. Apart from that I love the vehicle and am glad that I upgraded. When the crappy road tyres wear out I will be putting in new suspension and A/T tyres. Once this is done I believe that the vehicle will be a more than capable 4x4 for my needs.
In summarising, you definitely get what you pay for, and in the D40 case is as follows,
Better handling (no torsion bars, independent front suspension)
6 Airbags
ABS
Traction Control
Better seats/more room
cruise control
bigger more spacious tray
Better stereo/bluetooth connectivity (IPOD features, 6 speakers)
Child seat points
Utilitrack system in the rear tray
Dual climate control
central locking with remote access (key fob)
steering wheel controls
More kilowatts/power and torque
A down side of this vehicle is that you cannot fit a 2nd battery in the engine bay. I have not performed any towing with the vehicle yet and I expect as others have described for low down torque to be a little bit of a problem. I have heard people saying that they are required to ride the clutch etc when towing boats out of the water. if this is the case for me I will simply engage 4h or low as long your travelling in a straight line it shouldn't be a problem for 20-30 metres to get you up the boat ramp.
I feel that if you want a no frills 4x4 then go the D22 however if you want a vehicle with a few extra creature comforts and it is to be your main vehicle the ST D40 would be your answer. This is only my opinion after having owned both vehicles. I am sure plenty will disagree however but it works for me and my current situation.