I would highly recommend the Aqua cruise. We did this last year with Thomas Cook and it was excellent. You visit some very nice places on this route if you are the type that likes to spend time ashore. Kekova is a beautiful area, which you can only reach this by sea. It's a small village built on the site of partly sunken ancient ruins. On the top of a hill is a roman castle with spectacular views. Soe pictures of the area-

http://www.flickr.com/photos/madjap/url

I would agree that the trip down towards Kekova is much better. If you sail to Bodrum, you do quite a lot of early sails to cover the distance and also there isn't much to see on the coast between Bodrum and Marmaris. Doing the trip from Fethiye, you will stop at some great villages or towns (Kas & Kalkan) and also some beautiful sights along the way. Definately wouldn't bother with the one that goes to Symi & Kos as they are Greek and you have to spend far to much time in the harbours registering with the authorities when you go in and out of both Turkey and Greece. Marmaris to Fethiye isn't too bad either, but would prefer the Fethiye to Fethiye route personally. Have done 16 gulet holidays so far with just 21 weeks and 2 days to go to the next one.

On another note, whilst Thomas Cook are quite good, you don't get to pick which gulet you go on, its allocated on arrival. You could take a look at some other companies who offer greater choice. It depends on you budget really. Take a look at some web sites Exclusive Escapes are good but pricy. Blue Cruise have some good and some not so good with budget to exclusive options. Its good to call them, its a family run business and they are really helpful.

Hope you enjoy! You must be prepared to get along with everyone unless you are chartering the whole boat, in which case, there are a whole load of other options open to you.