Homeowners often ask about Paint finishes because there is a lot of information out there from different sources. Asking an experienced contractor who has been painting many homes over the years is your best advisor for what to do. Ceilings should always be done in Flat, to avoid flashing or showing starts and stops of rollers if hand applied. We recommend either Flat or Eggshell on walls. Flat will hide imperfections and is also good for walls that have lots of light reflection. and Eggshell is a 2nd option but you should be careful in where it is applied. We do see a lot of Pacific Northwest homeowners in  Gig Harbor and  on the Key Peninsula  using Eggshell often for walls. The best solution is to ask the advice of the painting contractor while he is in your home actually looking at it so that a recommendation can be made.