This questions has probably come up more than any other question throughout my last 15 years in the industry. Which is better, a flat, eggshell or satin finish? There is no definitive answer, but your lifestyle can serve as a good indication as which way to go.
For the record, I am a flat guy. I prefer the finish for a few reasons but the main reason is that I think it looks nicer. Nonetheless, I will attempt to withhold any bias and approach this subjectively. Before delving into this dilemma, let me state that satin and semi-gloss/gloss finishes will always be a better choice than flats for trim, moldings, doors, rails etc…, but we will focus on walls for now. Lets start by eliminating the separation between eggshell and satin. Yes, they have a slightly different sheens, but most brands of paint do not differentiate between the two. Some brands go from flat – eggshell – semi-gloss… while others go from flat – satin – semi-gloss… They will usually offer one sheen or the other, but not both. There are some other finishes that are available in between flat and eggshell/satin, which are: matte and low sheen. These are both nice finishes and offer an easier finish to clean and some possibility that they can be touched up (more on that later). These finishes can be hard to find in stock and only available from a few brands.
Pro and Cons
The higher in sheen you go up the chart, the shinier the paint will appear. The shinier your paint, the more durable or user friendly it will become. The sheen acts like a protective layer on your walls. If you were to spray a water bottle on a flat wall, than you would notice that the water tends to soak in to the walls a bit, whereas the same treatment to a satin or semi-gloss wall will have the water beading off much more. So, for example: a muddy or dirty hand print will clean up much easier on a wall with a sheen than one without. Although, as the sheen increases so does its lack of forgiveness. If you have a lot of wall imperfections, know that a sheen will show them off nicely. I would not want to paint a room with bad walls in a dark blue satin, because the darker the color and higher the sheen, the worse it will look. Also while finishes with a sheen are easier to clean, they do not touch up well. If you touched up a scuff on a satin wall (even with original paint); the paint may blend very nicely from a straight on vantage point, but turn your view to an angle and you can get a flash. A flash is where the sheen appears off a little, the touched up spot may appear shinier than the wall it was painted on, and that is because it probably is. This especially holds true on walls with lots of natural light. It can happen because the light can fade the sheen over time, but this can also happen on freshly painted walls.
Because of the better durability of eggshell and satin, if you have areas where kids and pets are prevalent than you may want to side with the sheen for those areas. Bathrooms and kitchens will also be good choice for a higher sheen, but if you have a kitchen where it shares some walls with a living/dining room, and you painted those walls flat, than go with a flat for the kitchen because having a line down the wall from flat to satin does not look very nice. I would definitely recommend a back-splash though.
Which lifestyle works best with which finish?
If you are the type of person to go around your home every so often and clean your walls or address the smudges when they first happen, than you should go with eggshell or satin. In the case of flat, if you are more likely to go around your home and touch up the walls, than the flat is your best choice.
When I painted my own first home, I went with a cream colored flat paint. I had thankfully purchased about 4 extra gallons., and about once every year or ever other year, I would go around my entire house with a roller dipped in the flat and touch up the walls. When I was done, the walls looked as if I just had them just painted (smelled like it to). I did this same thing three or four times and I only used about 1 gallon per touch up. I still had a little left over when I painted the walls a whole new color 6-7 years later.
On a final note, if you are taking on a painting project of your own; keep this in mind: When painting with an eggshell or satin, you always want to keep a wet edge (esp. in rooms with sunlight). This means that you would not want to cut-in an entire wall or two walls before rolling them out. You would want to make sure the cut-in paint does not dry before the roller paint is applied. Not doing this can lead to flashing between the wall paint and the cut-in. If you are painting a very large wall in a eggshell or satin than you may want to make sure that you have an extra helper. One person can cut-in as the other follows closely behind rolling out the walls. Of course if you choose a flat paint, than none of this really applies to you. You can cut-in a wall or a few walls at a time and roll them out after.
As always, Happy Painting!