Bryan,
Are there any advantages to the MP1 over the MM1? They look like the same thing, except the MP1 doesn't have the ability to monitor a separate feed from the mixer. I find it weird that they offer two products so similar to each other. I also can't imagine why somebody wouldn't want a headphone jack, so I figured there must be a reason that wasn't immediately obvious to offer the MP1.

The MM1 has the headphone amp and will monitor pre or line level. According to the site it's also bigger (longer). $50 difference.
Then for another $225 i can get the MixPre. Jeez i'm a gear slut!