What are the differences between the kits?

[LongRat]

Ok so on the Mardave site we have many kits listed. I'm going to buy one for circuit use, and I have had one before but stupidly sold it. However it isn't clear at all what the spec differences are between the cars even though I'm familiar with Mardaves.
A V12 race kit is £60, so what's the difference between that and the 'Sam Gray' VRX? Looks like a set of bearings, teflon hinge pins and a set of springs. This kit goes for £90. You can buy those separate items for less than £30 to upgrade from the £60 kit. So what are the other differences to make it worth the extra? And who is Sam Gray?

Then we have the VRX-CE. Fibreglass chassis, otherwise I can't see the difference between this and the Sam Gray edition. Is this right? What about it makes it better for circuit racing? I don't think any of these kits include a diff - is this accurate?
The site needs more information and the pictures need to accurately reflect the products. These are niggling questions that slightly spoil the fact that the cars are pretty good and cheap. A little more polish on the already greatly improved web site is all that is needed.

If somebody could answer my questions I will be able to make the choice on what kit to go for. Also no pics of the included bodies either...