I've dived both these quite a bit and in all honesty they are very different to one another. Assuming time is not an imperative as the journey time to Menjanan, road and boat is at least four hours from Kuta.
What type of diving do you like doing and what are you certified to dive?
Tulamben is a great site as there is so much from the shore all within easy reach. World class wreck, USAT Liberty, over 400 species recorded there, easy walk in and within a few fin kicks there is the wreck, can be dived all through the day, but really you need to stay at Tulamben, get into the water early before the day trippers and have it to yourself, some great swim throughs. Further along is the coral garden. And at the eastern end of the bay is the drop off, great wall diving, fantastic barrel sponges and some very rare marine creatures. Just around the headland is a great spot for seeing pygmy seahorses and going even further east are some good spots for critters. Great night diving, are you a photographer?
Menjagan, is all wall diving, interesting if you dive the right bit. If you like shallow muck diving and like critters then a visit to "secret bay†is a must and can be incorporated in a diving trip to this part of the island.
it is also important to get the right sort of company to help you with the logistics and I can highly recommend
AquaMarine Diving Bali they will be able to arrange all your diving, transport and hotels, there guides are first rate and if there is something in particular you would like to see, they will know where it is.
My choice would be Tulamben, simply because of the shear variety of diving and there are good hotels/bars to chill out when you're not diving. Plus there will be plenty of divers around to chat with and discuss the diving. Around Menjangan it is more isolated the chances of bumping into another diver is slim. Comeback if you have any questions.
if you can get a copy of this book, a bit out of date but all the right info for you,
Diving Bali
Posted: September 9th, 2006