Simon,
I have little knowledge of the hybrid variants so am not able to offer any advice. As others have indicated, the choice between petrol/diesel/hybrid might be based on mileage and journeys. In the past I used to work on 15K miles or above per year go diesel, less than 15K go petrol.
Both the Q5 and SQ5 come in traditional Station Wagon shape and Sportback shape. Personally, I like the Sportback shape but it adds to the price. I think the cost difference when new is about £2500 more for the Sportback version.
If you go for diesel, my choice would be the SQ5 Sportback in the standard "S" spec and not the Vorsprung. You can check what extra packs come with the car on a specific vehicle basis. The standard "S" spec for an SQ5 gets you the full leather seating and S-Line branding I prefer the 3.0L engine in the SQ5 range compared to the 2.0L engine in the Q5 TDI range.
If you go for petrol, my choice would be the S-Line 45 TFSi model, again in Sportback style and also checking if it comes with any extra packs. The standard seating in the Q5 S-Line 45 TFSi model is half leather/half fabric, I think the fabric is "Alcantra"?
Good luck with your search.
