Aysnc v Synch, is there a big performance difference?

Assuming in our system the graphics card will always be able to encode faster than the CPU will feed it data, is there any benefit to using an asynchronous encode over the synchronous one? I’m thinking the former will be far easier to get up and running and maintain, so perhaps I don’t need to try the latter. Assume the whole thing is running on its own thread, so is asynchronous to the rest of the software in general.