Originally Posted by Gardyloo

Welcome to FT!

Depends on the winds. Most of the time the prevailing winds at SEA are from the south, so the typical approach has you passing Mt. Rainier to the north of the mountain, hence the view is from the left side of the plane, then you turn final and can still barely see the mountain to the southeast; from the right side of the plane you'll see the Olympic mountains, Puget Sound and (usually) downtown Seattle and the Space Needle surprisingly close up.

However in the summer months the winds at SEA are from the north, in which case you get a quick view of Rainier, then the plane lines up for final from the south, meaning Rainier is on the right side and Puget Sound and Tacoma are on the left.

So pick the left side but don't be too worried, the views from the right side are pretty good too, regardless of the winds.

On departure, right side.