the two parts you get are conceptually much closer than in the second example.

I still don't see why this matters? To put things concretely, if I would be willing to buy the ticket in the first sweepstakes, why wouldn't I be willing to do so in the second? Sure, the uncertainty comes from different sources, but what does this matter for me and how much money I make?

The implications of "the probability is bounded by 20%" that you probably want to draw do not follow in the latter case.

If I understand you correctly, you seem to be drawing a slightly distinction here than I thought you were, claiming that the distinction is between 100% probability of a cow consciousness that is 20% as intense as human consciousness, as opposed to a 20% probability of a cow consciousness that is 100% as intense as human consciousness (for some definition of intensity). Am I understanding you correctly?

In any case, I still think that the implications that I want to draw do in fact follow. In the latter case, I would think that eating meat has a 20% chance of producing a really horrible effect, and an 80% chance of being mildly convenient for you, so you definitely shouldn't eat meat. Is there something that I am missing?

ETA: Again, to put things more concretely, consider theory X: that whenever 50 loaves of bread are bought, someone creates a human, keeps them in horrible conditions, and then kills them. Your probability for theory X being true is 20%. If you remove bread from your diet, you will have to learn a whole bunch of new recipes, and your diet might be slightly low in carbohydrates. Do you think that it is OK to continue eating bread? If not, your disagreement with the case for veg*nism is a different assessment of the facts, rather than a condemnation of the sort of probabilistic reasoning that is used.