In your experience, do certain hearing aids work better than others? My dad has one in each ear and still can't hear.

Hearing aid issue. There are two main issues when people lose their hearing 1) trouble hearing and 2) trouble understanding. People with long term hearing loss often have trouble understanding due to changes in the auditory pathway. If your father has had a long term loss and his understanding is poor then hearing aids may not help right away. Just because things are louder doesn't mean they are understood better.
Turn the noise up. Continued... A person with poor discrimination who is fitted with hearing aids will just hearing garbled sounds louder.. Very annoying. It would be like turning the volume up on a cracked/damaged speaker... Very annoying. Bottom line... See a reputable ENT who has audiology in the practice.
Yes and No. Some hearing aids are actually better than others. But hearing is complex. Hearing is measured with a pure tone level.. The beep, beep. And it is measured with discrimination.. The ability to actually understand words. A person may be a candidate for a aid based on pure tone loss, but discrimination may be poor <75% - not a good candidate for a hearing aid.
Hearing. Get another opinion from a hearing specialist located in and actual ENT office.