A straightener is much easier to straighten your hair but your hair must be totally dry before straightening. Straightening can cause damage but depending upon the iron you use, you can reduce damage to virtually nothing. A new iron I recently have been using in my salon is the Hana Elite 1" Flat Iron. It uses 100% Ceramic plates that distribute the heat evenly, rather than baked ceramic coatings that have less than 50% plate coverage.

Check it out if you're interested

Hana Elite 1" Flat Iron