Both are located in the Sierra Nevada (California) at the latitude of Fresno. The altitude is about 2000 meters for the Sequoia and goes down to about 1000 meters for the King Canyon.
In the Sequoia Park, you can drive and see interesting view points and hike as there are several trails. Do not expect large views because the park is covered by trees. Of course the most interesting trees are the sequoias, of which the "Sherman Tree" is the largest tree in the world ! The "Grant Tree" (on the road to the King Canyon) is just a little bit smaller. The road in the park is rather slow and there are not so many parkings.
The King Canyon park has a "V" shape ; there are not so many trees in this park but the views are spectacular. The road goes down from the Sequoia park and follow afterwards the river at the bottom ; you return by the same road. You find also trails especially at the end of the road. When I was there (October 2012) the Sequoia Park was in the clouds but descending to the King Canyon lets the sun appear.
Count one day to visit each park.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.