from what I can tell, the Thunder is just a regular SS with the S1 ssv wheels painted a different colour and some leather bits on the seats (leather bolsters look crap in my opinion). Which probably explains why it's the same price as a regular SS. The redline edition is a joke with the utes - and I really don't see the extra value in the SSVs either, now they all come with screens. For me, it would be between the SS (not necessarily the Thunder either) and the Maloo.
Considering you said you didn't want to modify it for a while, the upgraded shocks, better gearbox, million times better brakes, great seats, great steering wheel, pentagon wheels, hard lid, reverse camera and sensors and the 6.2 litre motor make the price difference worth it and helps you ignore the fact that the E3 maloo is quite ugly - though definitely the better of the two cars from the driver's seat when stock.