Hi Guy. We looked at the Terracan when we were hunting for a large 4x4. It is a lot of 4x4 for your money and the warranty is an obvious attraction. It reminded me of the Discovery, one which Landrover could have made between the current model and the last. It offers outstanding towing capabilities, but it's not the car we chose. For a long time I have championed the Sorento, even now, when we don't have one, I still feel it can't be beaten as a package. A smoother, quieter engine and apparently excellent auto (we had a manual) are just the starting points. Very comfortable to drive, the seats are very relaxing to sit in for hours and the controls work as you would expect them to. The base model has plenty of kit and is exceptional value, the XS and above has all you will need. Not for nothing has it won all the awards and the only way I could describe the decision we made is; If we had bought the Terracan, I would have always wondered what it would have been like to have gone for the Sorento. Having had the Sorento, I never wondered what ownership of the Terracan would be like.
As for fuel consumption, you should be looking at the low 30s on average, some will say higher and some will get lower figures, but as an average low 30s is just about correct.
It's a Rosy picture so far for the Sorento, but it isn't perfect. Soft metallics means that the paint scratches easily if abused. Handling while firm and predictable is old school 4x4, don't expect to out corner an X5. Resale values are patchy, but as you don't have to spend a huge amount in the first place, it's less of a concern.
Let me finish by saying you will be quite happy with either of these cars, so get a good test drive in both, to be sure which one you prefer.