Do hair straightening brushes really work?

My friend and I both tested the straightening brush (MiroPure 2 in 1).
My hair is naturally straight-ish with a tendency to frizz. Her hair is curly.
As a result, the brush worked better on my hair than it did hers. She wasn’t in love with the finish that the brush gave to her hair, and felt that it meant tugging quite a firm brush through her curls.
My hair fared better – it was a very quick way to get my hair feeling very straight and give a bit of extra length. Need to say I usually preferred the Dafni to using a normal set of straighteners.
What are you thinking?