None of the above.
Less cheeky answer:
I've always hated manifest. Nothing feels worse than manifesting a card you really could've used. From what I've found, most people like the idea but dislike it in actual gameplay because of feel-bads in losing a cool spell or planeswalker. This is less of an issue in shitty limited environs where the odds of losing a must-have card to manifest are outweighed by the utility of a 2/2 that might flip in a format that is largely defined by turning dudes sideways.
Carrier Thrall is frustrating because it's not a zombie and doesn't make a zombie token, which plenty of fun cards care about. I'm not often looking for ramp in my black decks, and if I'm going to have sacrifice fodder, I'd rather it be maybe a bit more relevant than a 1/1. The 2/1 body guarantees its role as end-of-the-pack draft fodder that -might- make the cut in a sac-heavy deck.
Ghoulcaller's Accomplice is
potentially the better of the three due primarily to having 2 relevant typings (human and zombie) as well as utility when discarded/dredged. That the token doesn't enter tapped it a big upside since that seems to be an obnoxious trend they're exploring. Obviously the sorcery speed limits the utility, but if I were going to consider any of these, it looks like the most interesting, serving a role to humans-matter and zombies-matter while also just being middling chump/sac fodder. I'm not excited to pick any of these cards most of the time, though, and paying
for a token that
might have a relevant type is a lot less sexy than getting one for free.
That considered, I think if your format is low-powered enough to be looking at these with interest, I'd pick the Ghoulcaller before the Thrall on the off-chance of synergies (human, zombie, discard/dredge) that have relevancy across at least 4 potential colour combos, but most of the time I'm just going to consider another card in the pack entirely. I would never take
Salty Misery because feelbad manifests are the worst.
edit: Actually I'll pick
Butcher Ghoul because relevant typing, still sac-fodder optional, and +1/+1 counter synergies if you care about that. Still pretty end-of-the-pack, though.