I am planning a cruise to Hawaii, probably around March or April 21. Which port would you recommend for departure (round trip) and why?

We will be flying in so having easy to get to accommodations for the night before as well as ease of access to the port are important.

San Francisco, Los Angeles or Seattle look like my options.

If I understand your question, you'll fly to the west coast, stay overnight, then proceed to the cruise port from there? If so, I suppose what you want to know is the proximity of the cruise ports to the airports?

For Los Angeles, thre are two ports, the World Cruise Port in San Pedro and the cruise port in Long Beach (a few miles away) which is used almost solely by Carrnival Cruises. Both are about a 40-45 drive from LAX and the same or a bit further from Burbank Airport. There is also an airport in Long Beach with more limited flights. There are scads of hotels near LAX, just don't stay in one in Inglewood. You could also stay in a nearby suburb to LaX like El Segundo (has a nice Hilton Garden Inn) or Manhattan Beach. Prime Time offers private shuttle services as well as others.
I guess my question is, why not fly to Hawaii and take the 7 night cruise that visits the 4 major islands and skip the time at sea?

I live in Seattle. I didn't even know there were Hawaiian cruises that left from our city! If the question is airport to dock transfers and maybe a one night hotel stay. Seattle works OK (about 1/2 hour SeaTac International to downtown). Would you leave from pier 66 (downtown) or 99 (a bit further north)?