We sailed on Allure fall of 2017 on a modified itinerary due to a few of the hurricanes impacting a few ports of call. We've sailed on a few other RC ships over the years (and Celebrity) but have not sailed on Princess and Carnival to be able to compare to.

We really enjoyed sailing on Allure because of the so many activities and places on the ship. The missus did the zipline and there was a one person wait. She also did the flow rider. They have two onboard: One for boogie boarding and one for stand up surfing. She did the boogie boarding on a sea day. There was about a dozen and a half people that rotating in line to do it. The line moved fairly quick because they split the flow rider in two sides.
Found the food generally only ok with a couple of winners here and there (eg Kummelweck Sandwiches at the Park cafe). We quite enjoyed the entertainment from the high dive show, to Mama Mia, to the parades/events along the Royal Promenade.
We generally didn't notice the crowds on the ship except for certain shows and events. It does pay to plan ahead to grab a spot early, book tickets ahead of time using the online app, etc.
There are a lot events catering to families/younger kids (eg. Shrek meet and greets, Madagascar show, etc) but just as in the movies, they throw in enough adult gags for a good laugh too.

In terms of itinerary, I feel the eastern itinerary is a little bit more exotic. Personally, I just want to avoid Jamaica though as both of our experiences there have not been fun. If you get a day at the cruise line's "private island" (Labadee or Princess Caye) it can be pretty enjoyable if you like an easy beach day.