Soft toothbrushes are better because?
They do not damage your gums,Do not erode enamel from tooth.Soft bristles are good to reach the inner corners due to its more flexibility.
They might not irritate softer gums as easily perhaps?
Well, they're good for starting tooth-brushers and sensitive gums.
That's what dentists recommend.
Soft brushes are maybe best used with young children who are just starting to learn how to brush. Exactly for the reasons given above.