Question you want to really ask is "what is the Best Best Best buggy for my driving style and level of skill?".
Owning the best isn't neccesssarily the gaurantee to wiin A-Mains. Honing on your skills to drive as well as the ability to tune your rig to perform to its optimum level will help you in the long run. I will gaurantee, even with the best rig out there, I will find myself in the wall since I am not a racer or do not race on a track regularly.
Some have older or "different rigs" and have taken them to the A-Main. Look at Greg Degani, he drove an Ofna rig other than the hyper 7 or 8.
If you ask me, a great rig to have is the one I have now or what ever I will have in the future. I currently own a nice SP1.