i want to get a buggy mostly for backyard bashing and maybe a little bit of racing. i've narrowed down my choices to the ofna hyper 7 rtr or pbs rtr and the ofna 9.5 mbx rtr. which buggy will turn the sharpest and be best for flat track oval racing? also, is there a 2-speed kit for any of these buggies?

HYPER 7 RTR is a great choice and you can put a 2 speed in it. my friend did and a cop buddy of his clocked it at 83 mph. thats NO joke. it is very durable and reliable. the os v-spec will make it scream.

2 speed isn't race legal so don't worry about that and it is also very weak and unreliable so i am told.
i would say go with the pbs but why do u want sharp cornering if it is oval track racing.