This is a question that is a bit difficult to answer because there are several brands that are really good. Of course it depends on the person also, but me personally I use the Cloud Nine straighteners or the GHD ones, this as an answer to the question "What's the best hair straightener of 2014?". They are both really expensive, but in my opinion they do the job properly.
The most important thing you have to be careful and to look after when buying a hair straightener is if the iron is a ceramic one or a titanium one. The ceramic ones are really good, much better than the titanium ones because the hair burn is not that intense. Keep in mind that there is no straightener on the market that will not burn your hair, so don't let yourself fooled by different people who try to sell you straighteners and they tell you that they don't burn the hair. They all burn the hair but if you use it wisely the damage to the hair can be repaired easily.