the good design satisfies all categories - it is functional, user friendly, esthetically apealing and, tehcologically solid, and comfortable in budget. creation of such complex composition starts with the concept. the designer together with the client defines the hierarchy of elements and categories. the more important factor subordinates all others. we call it "Priorities vs. Preferences".
on the other hand concept can refer to a more defined and pronounced design idea that drives the rest. see concept driven projects.