I will go with Hunt due to Lesnar's inactivity. 5 years is a huge amount of time to be out, and Hunt is an expert in spotting KO openings and setting people up to be KO'ed. If Lesnar stands for more than a minute or two Hunt is going to land something significant. Hunt's grappling is also underrated. Lesnar's conditioning also will not be where it was before.
That said, Lesnar's mma career decline was due mainly to his extreme illness and not being able to train or compete properly, and it would not be the first time Lesnar came into mma and immediately started smashing top people.