It can actually depend on why the person has the hearing loss and which hearing aide they choose to use.
If I was you I would search the different hearing aides and find out which one would be the most effective one to use due to the reason/s for the loss of hearing.
Just be aware that since this is severe hearing loss you may not get full hearing even with a hearing aide. It should be improved though to a point that helps the person to live a more normal life. Again this can be dependant on getting the right hearing aide for the job.
Some hearing specialists allow you to test 3-4 different aides once they have deturmined the ones that will give the most hearing benefit to the person involved. Being able to hear better is always worth it.