219 chain came about because the 10 Tooth Drive sprocket is smaller than the 9 tooth #35 chain. In Europe, where the 100 cc class runs direct drive, and turns a lot of rpm, they can get a lower ratio with 219 versus #35. The lower ratio, obviously, gets them out of the corner faster.
I've run both, with direct drive, is and saw no difference, other than being able to run a lower ratio. At some tracks that is an advantage.
If you race at tracks where that rear sprocket is getting really big, the smaller 219 rear sprocket could help you. There is no difference in the ratios, 15/60 is 4.0 – 1 with both, but the sprockets are smaller with 219.
If there is an advantage to the smaller 219 chain, because it is lighter, you couldn't prove it by me. In your case, only testing will tell for sure, but I rather doubt there is any speed advantage that can be attributed to the smaller sprockets and lighter chain.
From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)