Does he plan on doing the install and repair himself?
Unless he knows a plumber, I would think he would need to call a plumbing service.
I would be inclined to find the most reputable plumbing company, unless I knew that a place like Lowes had excellent service.
We would not go with Lowes for carpeting, but found out that they had a great contractor for roofs in our community, and good prices, so we went with them for our new roof, and they did a great job.
If Lowe's does the install, and he trusts Lowes, I would be inclined to go with Rheem over Whirlpool.
But I really am not an expert, and I don't know.
I just know that I am not too impressed with some Whirlpool products.
Have you tried doing some general searches like 'best hot water heaters', 'most reliable hot water heaters'.