I have only done one cruise tour. It was an Alaska Cruise Tour. We loved it. The land tour was a much smaller group of people, and we felt like we knew so many people by the time we got on the ship. It also gave me an idea of places I would like to go back to and spend more time. I'm sure I saw things and places I would not have seen of not for the land tour. Just make sure you do the land tour first and then the cruise. The land tour was a little exhausting and it was just so nice to then get on the ship and be pampered!
We've done Alaska, as well, and have an Asian cruise tour booked. We thoroughly enjoyed it,
and think it was well worth the cost. It did introduce us to a small set of fellow cruisers that
stuck together later on the ship.
It depends on where you are going and how much time you will have in port. We are very familiar with the Caribbean so when we are there and we have the time we book tours on our own and don't worry much about it. You always, always, always have to allow plenty of time to get back to the ship as they will not wait for you. If we are in Hawaii or Europe, we take the ships tours. That way, we know if there is a delay they will hold the ship. The only exception would be if we had an overnight stop. In that case we might go off on our own. The ships tours are nice but they do cost more than an independent tour. You will always find a lot of taxis in port who will give you a nice tour for a fraction of the cost of a ships tour. But again, be very careful of your timing. Negotiate the price before you leave the port. If you are going to a beach and want to be picked up at a certain time, you pay them when they pick you up, not before.