whats the difference?

 

A lockup converter has a clutch inside it. When conditions are right, the clutch gets engaged to eliminate the fluid coupling and create a direct link from the engine to the trans. It makes steady speed cruising more efficient. A non-lockup converter does not have the clutch. Therefore when you cruise along at a steady speed, there is still a slight slippage occurring in the torque converter. With all other factors being equal, a lockup will be able to cruise down the highway at the same speed but around 400 RPMs lower than with a non-lockup.

 

what do u think is better

 

I personally like the lockup converters better. You can run a big stall to get awesome off the line acceleration, but still get good cruising gas mileage. Best of both worlds! For all out racing though, I'd use a non-lockup. There's no need to have extra parts in the converter that add weight and increase odds of something breaking. Besides, who part throttle cruises in an all out race car?