I've never been to Tahiti but personally, Thailand is amazing. I've been three times in the past two years and it's always something new and refreshing. Lots of great beaches, cultural things to do, food, etc.
I'm going to Tahiti! We're staying on the island of Tahiti for one night (when we fly in) and then staying on Bora Bora for five nights and Moorea for five nights. We will have an overwater bungalow in Bora Bora, and a private garden bungalow with our own pool on Moorea. The hotels we are staying at are the Intercontinentals on each island. We worked through Tahiti.com with a travel agent to book everything. For 11 nights though we are spending over $10k. So be prepared to spend a lot of money with that type of trip! I have a friend who used to work on a cruise ship that would go to Tahiti and she told me of all the awesome things to do there. We will be going in just over a month so when I come back I can fill you in more about it!!
I have been to Tahiti! There is really nothing like it. I think it really just depends upon how active you want to be. Tahiti is a very relaxing, serene destination. Thailand is great for people who are a little more active. So, they're both great choices! But it really just depends upon how much activity you're looking for.
We had the same predicament ! I've always wanted to do Tahiti but when we really thought about it we wanted relaxation and adventure. I have friends that have been to Tahiti and they said it was pretty much just straight relaxing and fh and I would get bored. So we're doing Thailand and going to Bangkok, Chang Mai, Phuket and the Ko phi phi islands. So it's a mix of both. I think it really comes down to if u want more down time vs activities. Either decision you make is going to be amazing!