We flew nonstop from Atlanta to Honolulu on Delta and it was about 9 hours. Those who stop in California on the way often will stay the night and fly to Honolulu the next day, but I believe the flight from most cities in CA is still roughly 4-5ish hours. The additional time in the air flying nonstop to Honolulu is worth it to me in order to maximize your time in Hawaii, especially if you only have a week. The money you'd spend on a hotel in CA can be used to upgrade to the Comfort Plus or even first class seats if you can swing it. That makes the flying experience even easier. We flew in coach, but strategically chose a flight that typically flies a plane with a 2-4-2 seat configuration. This gave DH and I our own row so it was more comfortable. The plane has seatback TVs at every seat with hundreds of movies and TV shows, games, music. They serves us a hot meal, unlimited snacks and drinks - including alcohol. Again, this was all in coach. Could not have been a better flight there and back, frankly. I agree with PP too that a majority of flights are nonstop redeyes on the way home, which is also preferable to me because we just wanted to get home at that point. Hawaii is 5 hours behind Atlanta time, and 6 hours during some of the year as they do not observe daylight savings time.
If you're set on flying from the west coast, IMO, flying one of the major carriers will give you the best shot at a wide body plane and more comfort amenities. A carrier like Southwest flies from CA to Honolulu, but you're still contending with rows of three and bring your own device for entertainment. As far as where to fly from, LA will be among the cheapest options but LAX airport can be a nightmare, especially if you're staying in a hotel and returning the next day. San Diego will be a little easier to manage, but flights may be slightly more. At the end of the day, the difference in flight lengths and the price differences are going to be mostly negligible, so I would choose based on flight times and what's most convenient to you.