Dhow cruises are the thing for a visit to Khasab. We chose Dolphin because they have a good web presence and responded punctually to our email inquiries. I wish we had gone to another place, though the day we spent was fairly nice.
First price. Expect to spend between 15 1nd 20 OMR, or $38 to $50. Dolphin was for us 50 OMR, at the high end.
Second, convenience. Many of our cruise partners were picked up at their hotel, or maybe at the cruise ship that was there when we visited. That would have saved us 20 minutes of looking for the dock, though they did provide accurate GPS location.
Third, equipment. There seem to be two sizes of dhows, medium (~15M one story) and large (~20 M, two stories). We were on a larger two story dhow with a sunny topside (with no cushions or furniture) and a shaded lower story with some benches and cushions. We had no life jackets. For those of you with a penchant for not dying in a marine accident, well, I don't know. I doubt that any of them had safety equipment. We brought our own goggle and snorkel, but there were no flippers. It turns out there is not much to see underwater either, though it's good to get a little swim in. They provided showers on the back deck and towels too. Note that there is really no place to change your clothes if you are taller than 4 feet.
Fourth, itinerary. They all seem to go the same place, up the fjord just N of Khasab where telegraph island is. All of them look for dolphins and go snorkling. However, as another reviewer said: "They waited for us while we went to an ATM!!" Consider what that means for the other 30 people on board, 45 minutes of unexplained waiting while all of the other dhows started their cruise. Coupled with coming back 45 minutes early for no reason, that means that the "whole day cruise" was about 5 hours. That was enough anyway.
Fifth, food. They had cold drinks and fresh bananas, apples, and oranges out all the time, and some overcooked chicken and rice, which was adequate.
Finally crowds. Dolphins Khasab was less crowded, by far, than the other dhows we saw; we had maybe 35 aboard, and the other big dhows had over 50. That's a plus, but the other dhows would have been fine too.
Were I to do it again, I think I'd have gone down to the dhow harbor around 8:45 and looked for a well-equipped dhow with staff who spoke English, and gotten on board. There are plenty of dhows and all of them will likely show you a good time. Some for 15 OMR, and others for 20 OMR.
p.s. the coordinates of the dhow pier is: