I agree that as you defined the problems, both have problems. But I don't agree that the problems are equal, for the reason stated earlier. Suppose someone says that the boundary is that 1,526,216,123,000,252 dust specks is exactly equal to 50 years of torture (in fact, it's likely to be some relatively low number like this rather than anything like a googleplex.) It is true that proving this would be a problem. But it is no particular problem that 1,526,216,123,000,251 dust specks would be preferable to the torture, while the torture would be preferable to 1,526,123,000,253 dust specks would be worse than the torture: the point is that the torture would differ from each of these values by an extremely tiny amount.

But suppose someone defines a qualitative boundary: 1,525,123 degrees of pain (given some sort of measure) has an intrinsically worse quality from 1,525,122 degrees, such that no amount of the latter can ever add up to the former. It seems to me that there is a problem which doesn't exist in the other case, namely that for a trillion people to suffer pain of 1,525,122 degrees for a trillion years is said to be preferable to one person suffering pain of 1,525,123 degrees for one year.

In other words: both positions have difficult to find boundaries, but one directly contradicts intuition in a way the other does not.