Linda S, I would prefer the Island Princess for one reason: the Horizon Court is up high and all the way forward instead of aft like Diamond Princess and the views are spectacular. The views are actually spectacular from anywhere--but it can be very cold, especially in Glacier Bay or Tracy Arm--anywhere there are glaciers; and it is so nice to relax in the comfort of the Horizon Court and soak in the scenery.
In my opinion there is not one whit of difference between July and August; wildlife sightings, like the weather, are completely unpredictable and capricious. Go when it best suits your schedule.
Upper decks would be better for wildlife viewing; your field of view is wider and it's easier to get from side to side when sightings are made.
We have been on all of these ships and love both the Diamond and the Sapphire as they are both built the same. These are sister ships. We hated the Island as it's smaller and we love a bigger type of ship. We went to Alaska the middle of June and love it. The weather was nice and sunny at every port and the temperature was nice. We never had to put on any extra clothes. We had a upper balcony which was very nice. We found the buffet area on the Island to be small and not as big as variety on the other ships. I guess you could call us BIG SHIP cruisers. Also in June we found there were less kids on board.
Anything in particular? I love Sapphire Princess. I've been on Sapphire Princess and Island Princess numerous times. I like Island Princess for Alaska for the reasons I mentioned, and also for the Panama Canal--especially since Sapphire Princess is too wide to travel the Canel :-). But I have been to Hawaii on Island Princess too.
The ships have slightly different deckplans but the venues are very similar. The cabins on Island Princess are just slightly smaller but the open deck areas seem more spacious and uncluttered. The food and service and very comparable. I think Sapphire Princess makes better use of its aft deck space. Both are beautiful and well maintained. I'm sure you would enjoy either one.
Wooddon, you are right that Island Princess is smaller; but I would like to point out that it actually has a larger passenger-to-space ration than Sapphire Princess: Sapphire Princess is 43.44 while Island Princess is 46.7; I've always felt like I have a little more elbow room on Island Princess.
I think we are going with Sapphire in August, 2012. We are planning on a 7 day tour starting in Fairbanks followed by 7 day cruise.
We are going to get a balcony room for the fantastic view I am expecting. Any recommendations on level or specific room? I've heard some room balconies look into other rooms/balconies. I would prefer to not view others or have them view me. Also, which level would have a "covered" balcony in case of rain?
If you want a covered balcony and don't want to view other balconies your best bet is Aloha or Lido deck. Or if you want a mini-suite, the ones on Emerald Deck have covered balconies. Your best value would be a Catagory BC cabin on Aloha Deck.