If you want to see the slough wildlife, this is perfect. We originally planned to kayak, but the logistics and timing didn't seem favorable on the actual day, and we were able to snag spots on an 11:15 departure (which gave us mostly sunny skies). I'm so glad we did this instead. Not only was there no worry about tides, timing, or currents, but it was very easy to reach the wildlife and to take pictures--and we took lots. (With a 400mm lens, my son was able to take some pretty nice pictures of otters and birds. If you are a serious photographer, the last seat in the boat is the best, and we were grateful the captain, spotting his camera, seated him there.)
We saw more sea otters (well over 50) than I have ever seen at once, including two pups, lots of harbor seals, elegant terns, pelicans, cormorants, sea lions, a peregrine falcon, and much more. The naturalist and captain worked seamlessly together to make sure we saw everything while being respectful of distance, and hanging out long enough for everyone to spot the creatures, and the slight elevation of the boat made it easy to spot creatures across the water.
If you kayak, you would have to spend a lot more time to see what we saw and probably would have missed a lot, even though you would have the option to get closer to the shore and go deeper into the 6 mile slough (we went in about 2 miles). We might kayak another day, but in the time we had, I am thrilled we did this.