I have a Kenwood food processor and a stand mixer. Can't rate them high enough, but I really, really like cooking.
The food processor really only speeds up prepartion time, but let's you do some other nitty things. Raise egg whites while you mix the remaining batter for cake, super fast potato purée, marinade sauce is a breeze to prepare and better than pestel and mortar + hand mixing, etc. The stand mixer is a real killer for all things batter and dough, especially thoose that take a little longer to knead.
If i had to pick one, I'd take the food processor with a dough and mixer attachment (Kenwood has them, not shure if sold separately).