What kind of riding do you do and where do you typically ride? I don't know much about your board or boots, but I currently ride the Factory bindings after having ridden the Missions for my first couple seasons, so I might be able to offer some general insight. There are people here that can give you more detail, but they'll want to know what your riding style and conditions are.
In my opinion, the Missions are definitely more playful while the Factories are much stiffer and more responsive. The Factories are also more comfortable in my opinion. They are better suited to hard-charging and freeriding than the Missions are, even though the Missions work pretty well in that regard too. I'd say if you are all-mountain but tend to do more park/freestyle stuff then the Mission is probably fine. But if you want more response and something stiffer, then get the Factory. But don't buy it if you are just trying to round out a complete "Travis Rice" setup.
I think the Mission is a good binding if you can get it on sale. I still use mine from time to time.
Drinking the Kool-Aid:
2013 NS Heritage 166X
2014 Union Factory