Here I go again. I preface this with, I don't work for Princess. We've sailed on NCL, RCL, HAL, Carnival, Costa, and Princess. To me, personally, Princess is the best. We've only been on the Dawn, Sea, and Sun and are going back on the Sun this October. So far, the ships have been immaculate, the service impeccable, and the food has been great. There are plenty on this board that will disagree. The choice of cruise line is totally subjective, what I like might be horrible to someone else. The best advice is to seek a travel agent that is a cruise specialist. They would be the best to match your needs/desires to the proper cruise line. Just my 2 cents, I like Princess the best. No matter which ship you choose, have a marvelous time!
I've been on both ships. They are both very nice ships. The Diamond is one of my favorite ships (along with the Island/Coral Princess). In general I prefer Princess to Celebrity for several reasons:
I prefer the flexibility of Princess' anytime dining. While Princess does offer assigned seating (which is comparable to Celebrity), Celebrity does not offer anytime dining.
I prefer the layout of the Princess ships.
I like the fact that Princess has smaller dining venues. While Celebrity's single main dining room (with 2 levels) is impressive, I enjoy the smaller dining rooms on Princess more.
While Celebrity has a great reputation for it's food, I think it is just as good on Princess--and I like the menus better.
I like the freshwater pools on Princess. Celebrity is saltwater.
I like the fact that Princess has self-service laundries. Since I have enough cruises to get free laundry and dry cleaning from Princess, I don't use the self serve laundries anymore. But I used to find them useful, especially on longer cruises.
Anything other than Hawaii, I'd rather go with Princess. However, if I were to do Hawaii again (I have cruised roundtrip from Honolulu on NCL, and roundtrip from LA on the Summit)--I would fly to Hawaii, spend a few days in Hawaii, and sail roundtrip from Honolulu or Maui on NCL. I prefer the extra time in Hawaii to the sea days to and from the islands. If you go roundtrip from the mainland, more than half of the time is transiting the Pacific. And first few and last few days can be rough and chilly. Not good if you want to use the pools. Also, the newer NCL ships that just do Hawaii are very nice.
Tuuuuf question! Diamond is an upper end Princess ship (I sailed sister Sapphire) while Summit is Celebrity's top tier Millennium class. You can't go wrong with either.
However, be forewarned, if you sail Princess you'll miss the truly world class Normandie, the Summit's specialty restaurant and one of life's greatest pleasures. Those nights in the specialty restaurant (always book TWO nights!) are the stuff dreams are made of, not to mention great conversation and memories for years to come.
The Princess line, and this ship in particular (if it's anything like the Sapphire) has its own strong points, which I can address later if you're interested.
Would like to mention that jjf50's remarks (just above) are right on. In addition, Princess allows wine/champagne to be brought on board, no problem, no questions asked. That's becoming an increasingly sensitive issue for other cruise lines.
In addition, sailing Princess more than a few times (6 actually) merits full internet access free of charge. Celebrity is charging .70/minute, and does that add up!
Speaking of which ship, does anyone have an idea on what time of year is the best to cruise the Princess 15 day intinerary to Hawaii from LA? I want to do this cruise but want to miss all the storms and rough water
Not much to add; I agree with everything that was said about Princess. I've cruised with them for over 30 years and always had wonderful experiences. The ships are all great and Diamond Princess is one of the best. I would recommend Princess without hesitation.