Odd question really ..
Neale, if you're planning on running at Mendip, then as a relative 4wd newbie I can recommend the 4wd class. We've had some really good close racing over the winter and the 4wd just has more grip than a 2wd on wet astro, its not easy to drive just easier !!
And then get a 2wd for the summer ... doesn't matter which one, they're all good, and then stick with one car and get it setup properly ... job done