Definitely search the threads.
This is a topic that doesn't have a blanket answer for every horse - much like the treed vs treeless saddle debate.
So..."it depends". There are various kinds of bitless bridles out there, not including various types of hackamores.
Aspin231 wrote an amazing post for me describing the mechanics of the different types of hackamores, which you can read here: Hackamore question - shank shape
Here's a decent article about the different types of bitless bridles: Natural Horse World Bitless Bridles
It may take some experimenting before you find something that works, and your horse may never take to it. Some don't, but most do. Read up and use what you know of your horse to try to make an educated decision before you start making purchases.
In my personal experience, my horse doesn't like bitless bridles. He doesn't like the pressure on his head. He does, however, enjoy his hackamore.