I don't want to "knock" the fishing tours offered by Princess... I run them once in a while here in Juneau too. If I were booking, however, and wanted the best experience possible, I would book something directly with a charter captain who I could talk to directly. When you book via the cruise line, realize that you're booking with a sales agent (Princess) who will get a 20-30% commission. They then book you with a tour broker (one in each town) who takes a 20-40% commission. By the time you get to the boat, you'll get a crew that's getting something in the neighborhood of $80 or $90 (out of the $200 you paid) to be in charge of your entertainment and safety for 4 to 5 hours. Personally, I would prefer to just give the same $200 directly to the boat captain and get the same tour.
When my family travels, part of the fun is my kids choosing the name of the boat we go out on too. Not that you want the kids choosing to go fish on the "Happy Hooker" because it's a cute name... (Knotty Lady?) but the cruise lines (and often the brokers themselves) have no knowledge of the boats, or any possibility of selecting a specific boat.
Look at the 5-star link I posted above. It's really just personal preference, but knowing what I do about the business, I don't really want to be on a boat that isn't on "the list" with a 4 or 5-star rating. You can get into this business with a $20K boat, or you can get into it with a $250K boat... do you want the guy who just tossed something together, or do you want someone who goes the extra mile to be sure you're happy, comfortable and safe?
Ketchikan does have good salmon fishing. For the time of year you're coming, I don't think there's a town in SE Alaska that doesn't have good salmon fishing. It's peak season everywhere, and you'll have a great time in any port. Schedule it where it fits your other touring best.
Oh, and don't buy into that whole "don't go with a non-ship tour... what if they run late and you miss the ship?" Tour operators up here live and die by the cruise ship schedule. If your ship is departing at 3 pm, the charter boat should have you back there by 2 pm at the latest. Call a few boats and see what they suggest. Also, be sure to check on the refund policy in case your ship is late or changes itineraries on you at the last minute. Most folks are very "fair" about that sort of thing... if it's out of everyone's control, you aren't likely to pay any penalties, and you'll be able to re-book or get your money back.
Hope this helps some...
Better not for now... signatures get me banned!