Are U-shaped brushes appropriate for the elderly?

My husband, mid-70s, has multiple health issues and sometimes struggles with brushing his teeth. He typically brushes 2-3 times per day, has never flossed, yet is blessed with whatever it is that makes some people have fewer problems. He has all his original teeth, no crowns, has had only a few cavities in his life.

He has had a few periods of burning mouth syndrome, but the last was several years ago.

When he can't stand, he will brush his teeth sitting up in bed, but he hates doing that and is more likely to avoid brushing when that is necessary. I thought maybe the Auto Brush (ADA approved) or the Sonic Brush V5 might be easier / more convenient to use.

I thought I remembered that initial reviews of the U-brushes said they were kind of useless, but now opinion seems to have come around a bit.

If he likes his, I might get one for a disabled sibling, too.

What do you think?