They are both sidewinder (side engine) racing kart frames. Low to the ground with the expensive wide tires and other components. Personally I prefer vintage style rear engine karts with skinny tires as the tires are easier to break free and it's easier to drift and "fish tail".
These racing karts can't even handle a speed bump without getting hung up.
Build on the one that's prettier or in best condition.
Again, where's the pics? I don't believe you have either of these karts....yet.