Capri Boat Tour Recommendations

We are taking a cruise (early May) with an all day stop in Capri. I think that we would like to take the popular 2 hr boat tour around the island (with a stop at the Blue Grotto). There are lots of companies offering similar trips on Gozzo boat for 6-8 people for 150 to 200 euro. Any recommendations on what company to choose?

We used Whales di Wendy. I can't believe how much we saw in two hours. The captain knew the best places for photo shops. He drove into all the grottos except the Blue Grotto. It was comfortable, private and we felt very safe.

is it necessary or recommended to book in advance? I worry about booking a boat trip in advance and then find the weather is bad. But I also worry about not booking in advance and not being able to get a boat when we arrive. What was the capacity of the boat?

Here's their contact information. We paid at the end of our trip. There's various sizes of boats. Ours was the smaller, holding 6-8 comfortably.

http://www.capriwhales.it/?lang=en