I am a resident of Newport Beach. This is just a review of the full service options in the Newport/Costa Mesa/Irvine vicinity.
The nicest hotel in the Irvine vicinity probably is the Westin South Coast, which completed a room refresh in 2005. The nearby Avenue of the Arts Hotel (Tribute Portfolio) recently completed an $18 million refresh and probably is the second nicest in the vicinity, but many rooms and suites still feel dated; that hotel is building a new 15 story tower which will add a lot of very modern Deco style rooms to the area.
After that, it’s all about cost-benefit and priorities. The Marriott Newport Beach in Fashion Island is higher demand due to its convenience to that mall, so its rates are almost always higher than that of the less convenient Marriott Newport Bayview—despite the Bayview having slightly larger rooms and perhaps being the slightly nicer property. The Irvine Marriott is a solid choice and has a good location.
The Ritz Carlton and Marriott Newport Coast Villas are unquestionably the nicest Marriott portfolio properties in OC, followed by the Lido House (Autograph Collection) on the Newport harbor and the Laguna Cliffs Marriott in Dana Point. But all of those are coastal and not as interior or as convenient to South Coast Plaza or John Wayne Airport as the other hotels mentioned.