This is probably best determined by your budget and time constraints!
The bonus of a liveaboard is less time travelling and more on the reef and the liveaboard tours take you to places that are too far for a day trip so this does mean they are a more pristine and quieter option than some of the more heavily visited reefs. They are a chance to really explore and experience the Great Barrier reef in a unique way to the average diver.
That been said there are loads of day trips on smaller boats that will take you to sections of the reef where your boat may have the reef to yourself at certain times of the day.
I’m not a diver (I have only done introductory dives) however I have seen turtles, reef sharks, clown fish etc on many of the day trips out of cairns and the Whitsundays. Generally if you avoid the larger or pontoon boats then you will have a far quieter experience as the smaller boats can access moorings that the large boats cannot.
Day trips on smaller boats depart from many of the towns and cities along the east coast of Queenslands, particularly places like Cairns.
Visit Queensland has some quick blogs on their website for some more information!