My wife and I stayed there 5 nights for our honeymoon in August 01. Hands down, a spectacular resort. The Fairmont Kea Lani was just an awesome place to be. (Side editorial comment...it blew the pants off the Marriott on Kauai where we spent our second 5 nights).
OK - couple things. I'm a late 20's guy so have lots of friends who have been honeymooning out that way. Best friend spent Sept 2001 at FS, another friend went to Princeville Resort in 2000. We all seem to think they were all very nice.
As for FS vs Kea Lani vs Ritz vs Grand Wailea. The single most important reason to take the Fairmont is that the hotel (last time I checked) was all suites - so using your suite upgrade will just get you a better suite. I can't tell you how much I value a suite - its the most important thing to me. So you win there in my mind on accomodations - being our honeymoon we actually went all out and PAID (cringe at the word) for the corner ocean view suite. It was worth it. Over 800 sq feet, and yes the bathroom was spectacular. We did walk over to the FS and it looked stunning in the common areas and I am sure the rooms are top notch too - my friend confirms his 10 nights there were stellar.
That said, check out the latest Conde Nast Gold list and you'll see most recently the Kea Lani scored a perfect 100 for service. Yet another big win.
I can't honestly say that I know for a fact its better, but you cannot go wrong at the Fairmont! As far as pricing - I think its pretty common in Hawaii these days, but check for some sort of 5th night free award to help cut the costs. Enjoy!