There are two rooms and only one key. One key leads to 3-4 things for the player. The other leads to a single item contained in a chest?
The room with 3-4 things always seems like a pretty good deal, as opposed to choosing a chest. After all, how do I know that what is in the chest is worth as much or more than those 3-4 things?
Under what circumstances is it better to choose the mystery chest over the 3-4 rewards? Why would anyone choose the chest instead?
If my run desperately needs a healing potion or sorely lacks a remove curse scroll, I may opt for the knickknack side; otherwise, the sole mystery chest is what I typically choose as it pays off more in the long run.