Even if you get the hyper 7 you won't be dissapointed. They are both good buggies.
The Hyper 8 beats the hyper 7 slightly on geometry and adjustment but you can still go out and win club races with a hyper 7.
As for upgrades,(assuming you get the RTR of either) CNC Chassis braces, new steering servo, receiver pack and turnbuckles all round. that should get you started. then go for CVD's and add anything from the pro kits (of each version) when you get the money/ break something.