Bora Bora/ Moorea

We will visit French Polynesia next March for 9 days. What would your suggestion be to do in that 9 days? Is it worth it to buy a ticket to Bora Bora or is Moorea as beautiful?
Any suggestions on nice diving spots over there? And costs?

Thanks a lot

What would your suggestion be to do in that 9 days?

Eat, drink, dive, and be merry. If "we" means a "significant other," you can figure the rest out for yourself.
Stay in the Sofitel Bora Bora Private Island and you can literally snorkel in coral gardens right off of the back porch of your over-water bungalow. Getting to Bora Bora with scuba gear presents weight problems on the airplane. I don't think you need scuba in the lagoon which is where all the resorts are. There are guided dive tours on Bora Bora if you want to go on one. As for costs, I'm tempted to say that if you have to ask you can't afford it. Do some research. Bora Bora is not "cheap."

Is it worth it to buy a ticket to Bora Bora or is Moorea as beautiful?

Both islands are incredibly beautiful, at least to these North American eyes. James Michener called Bora Bora the most beautiful island in the world. I can't disagree with him. You can reach Moorea from Pape’ete by ferry boat. Bora Bora is about an hour away from Pape’ete Tahiti by commuter plane.

Be aware that March is in the "wet" season in French Polynesia.

Enjoy!