I haven't dug into Mousetrap, but I made Keypress because I needed/wanted the arbitrary modifiers and counting combos features which mousetrap does not have (and also Mousetrap hadn't been released yet when I started work on this). Keypress also gives you a lot of control with the explicit options like is_exclusive, prevent_default, prevent_repeat, and is_ordered. The prevent_default option for instance will prevent the default behavior on all keys that are part of a combo if it thinks you are working towards a combo (for instance, when pressing up + right, both keys events will have preventDefault applied).

As I mentioned, I didn't actually try using Mousetrap, but from looking at the documentation Keypress should have at least the same features and then some more very specific features that are probably only useful for games.