As the OP can tell, saddles can be like music. The number of opinions are only limited to the number of riders or listeners. Each person has a different experience. It is an impossible challenge to tell you what your Dad will find comfortable and like.

Mtnbke wants to free willy. I find traditional leather saddles so comfortable, either a Brooks, an Ideale, a Sprint, or a Wrights are on all my bikes. I find any gel saddle, as loose spoke mentions, to be very uncomfortable.

I ride several different models and find them all to be just as comfortable. Three of my favorites to ride this past year included the Brooks B5N, the Colt, and a Wrights W5N.