My gut reaction is Hall, but some analysis could probably get us close to a definitive answer.
The questions is really, how fast could each of these athletes currently run an all-out, non-tactical mile - which would lead us to the answer of who is faster. We assume that neither is doing anything beyond whatever their current training regimen (or lack thereof) is to prepare for the race and that both are in good physical health, willing to go hard.
WVN is the more known quantity here. Though he's never run a serious mile to my knowledge, we know that he is at peak fitness at an event that requires some aerobic fitness, but that he probably doesn't do any specific training non-sprint distances. For a sprinter, he is light and small, so the main thing holding him back is his lack of mile training/natural ability. I say WVN could hit a ~4:10-4:20 mile if he had someone to key off of (I say he does worse in a TT because pacing is something that is practiced in distance training, which he presumably doesn't do).
Hall was never a miler in his prime as an adult, but has run sub-4 as a teen, meaning that he likely has a good amount of natural ability. He also has the "memory" of what it feels like mechanically and physiologically to go hard in a mile, which could be a key factor when racing someone who lacks this. So even if Hall is out of shape and over race weight, I still say he runs a decent mile based on pedigree and confidence. I'd slot him at 4:10-:20 as well, but maybe give him a slight edge because he is more familiar with the race distance.