It's simple if one means seeing the flash of lightning due to the speed of photons relative to percussion of air. On the other hand, if one means the time it takes for lightning to travel from the cloud to ground, I don't know the answer scientifically offhand. Lightning is still an electronic discharge, so it's probably faster, but not for the reasons given (Look up one of Maxwell's laws I believe regarding the velocity of an electron over distance). This assumes I am answering the question or misinterpreting.