As stated at the beginning of this judgment, both entries have some things that appeal, but also both have some rather pointed weaknesses.
When it comes to being able to use either entry, I would judge them to be about equal, though for different reasons. Both present solid ideas upon which an adventure could be built, but both also have some flaws which would hamper this, though in different ways.
I’ll start with Snake. The set-up here is not a bad one. You take a group of individuals, drop them in the jungle and then reveal they are actually being used to help with an arcane rite to summon an evil god’s minions. Snake provides this great set-up, a nice scenario for how it is going to play out from the cult’s perspectives, and even a decent concluding scene. But what we don’t have are ideas for what is going to be happening to the PCs from day to day. We have a beginning and an end, and a path for the NPCs, but we are missing encounters, occurrences and events which might clue the PCs into the whole going on. The PCs are interns but what are they supposed to be doing the first four days while the cult is doing its nefarious deeds? I like the premise well enough to want to know, and maybe even would want to use the premise, but its going to take some work to fill in those details.
Sourdough, on the other hand, is better set up in regards to what the PCs will be doing and why, but there are some problems with how its going to play out. Firstly, as an adventure, its basically a single encounter. The PCs are asked to find a guy, read a note and then find themselves in a jungle on the other side of the world where there is a party. An hour later, cakes and what-not are attacking, the PCs find themselves stripped of weapons, armor and clothes, and then there is a sword that suddenly appears. One sword. For a party of maybe four PCs? Not counting spell-casters, I’m not sure that this is going to be fun to actually play. It is generally better to allow the PCs to show off what they have (saying yes) then to simply nerf them for the fun of it, because this is not always fun for the players. Players don’t like having things taken away from them. It is generally better to start off from a position of nothing and then allow PCs to improve then to suddenly drop equipped PCs down to nothing. As well, if the PCs have magical gear then that gear is going to probably get a save, or some-such, which undoes the premise. There is also the difficulty of level-appropriate encounters. The set-up says that it is low-level, but the big bad is a lich-level wizard? Sure his spells are more appropriate to the kitchen, but still, the PCs are naked, defenseless except for one sword, and probably out of spells by the time he attacks, and he’s fresh full of spells. I can see that ending very badly almost every time.
All those complaints considered (and I want to reiterate that I still see the gems sparkling down in there in both entries), as a plug and play, I think Sourdough has the edge, and its enough of an edge to push it in the point race, just past Snake. For the moment.
So what about the last criteria – the fun factor and personal preference?
Snake appeals to me, but not completely. Because I like Cthulhu and mythos scenarios, I am perhaps a little more critical of them. In point of fact, I have two knocks against the adventure as presented. I like the general premise, the set-up, and even the time-table. But it is hurt by two things. One, it is a little too flippant and not in a way that helps it. There is a certain sloppiness to it. Let me make a number of illustrative points. Fleischman’s yeast, while currently owned by a British company, is marketed, according to Wikipedia, only in the US and Canada. Yogurt Cakes are not made with yeast, but with Baking Soda. And when you start using real people, and real companies, it has a chance of bringing out the worst in a certain kind of player. I would have preferred parody names to real names. Mythos wise, I am not sure why Yog-Sothoth is being used as the big bad and not Yig, and the yugg-urts, though a clever pun, should have simply been yuggs and there should have been a little more motivation then simply cool cannibalism and flesh eating monsters. There also was a missed chance in not better tying in the yeast to the mythos in some way.
On the other hand, Sourdough has an initial appeal to me, but the more I contemplate it, the more it falls apart. It is, in a word, heavy-handed (that might be two words). And not heavy-handed in a good, or subtle way, but in ways that smack the players up alongside the head with the fact they are being railroaded. They read a note and get teleported. Their clothes and weapons falls apart. They have only a single way to attack the monsters. There are no meaningful choices at any juncture along the way to even provide an illusion of control to the players. I like the idea of a baker trying to achieve immortality through the use of magic yeast and a demonic wager, but from the players perspective all we have is a fight with cakes. There is no build-up, no foreshadowing, and again, no choices. It’s a fight they either win or lose, depending, and that’s really it. Granted, they are then stuck in a jungle on the other side of the world. And that is an interesting set-up for interesting adventures, but it’s not this adventure.