RayPaK/Rheem/Ruud thumd up they are all the same manf. with different lables.
Jandy is good too.
Pentair Master Tems/Sta-Rite Max E Therm are good. Same heater with different badges and skins.
Hayward's newer model is too new to say. Past Haywards have been ok but still come in 4th in my book.

Thank you so much, poolguynj!
I would appreciate more views and experiences with these brands. If I choose the RayPaK for example I would like some good reasons to give the installer for not going with his recommendation of Sta-Rite. It would also be helpful to understand why low nox is not a plus.
From loyalty to my PB, and because choosing Hayward would extend the warranty, I would prefer to have him provide and install the heater, but do you think these reasons are outweighed by the inferiority of the Hayward heater?
With so little knowledge and no experience it is difficult to make the right decision! I realize that in the scheme of things choosing a brand of spa heater may not seem important but for me like many others, especially now, every decision has to be carefully thought through.

Are you buying more than just the heater to get an extended warranty? Most manufacturers require 3 thing be purchased at the same time like a filter, heater and pump.

Low-Nox doesn't make a significant difference to the atmosphere. It does to the wallet though. If I remember right, California repealed this former requirement.

The Ray Pak and Sta-Rite are about equal in owner satisfaction. Either will serve you well.

We already have the Hayward pump and filter, I think you are correct in thinking that Hayward requires 3 pieces of their equipment to be purchased to qualify for the extended warranty. The heater would make 3.
Thank you poolguynj for reassuring me about the quality of Sta-Rite in comparison with RayPak. My choice now seems to be between Hayward (with the benefit of the extended warranty) or Sta-Rite.

The 3 pieces must be purchased at the same time or if a rep gets involved, within a year. Simply having for example, a 5 year old pump and filter doesn't qualify to the best of my knowledge.

I would love some confirmation from someone on that please.

The newest Hayward heater may turn out to be the best ever, but based on previous models, don't count on it.

The Sta-Rite and Pentair models are identical, one is round, the other a cube. A good heater, and very compact if space is an issue.

Raypak is an excellent choice. You may have heard of their sister company, Rheem.

A Jandy LD is an excellent choice if you don't need/want a digital display.

Avoid headaches and don't buy from the internet.

"You may have heard of their sister company, Rheem."

You mean parent company.

Thanks for the all the advice poolguynj and for yours, mikethepoolguy.

Our new RayPak heater is now installed. The installer is still issuing dire warnings that the pilot and the heater outer casing will rust out quickly (he calls the heater a "RustPak") and says that we will need a high wind stack. Our local dealer says he never sells high wind stacks for Ray Paks! Time will tell but after reading all the info/comments on heaters on this site I feel confident that we have a good heater. Thanks again guys!

Wish you went for the electronic ignition.

We did. Model # PR406A EPX.
Our installer also tells us that the cupro nickel (that I had specified because I believed it would withstand the hard water and salt water conditions better) will not actually last a long as the copper tubes because the cupro nickel tube walls are thinner. Did I goof?

90/10 cupro nickel is harder and will last longer. It is not bullet proof however and chemistry must be well maintained.Raypak also has a ASME heat exchanger which is thicker but pure copper.

I've been trying to get a Raypak 400K ASME bought and installed since late last summer. No one has called back. Sort of amazing since everyone is moaning about things slowing down.

I'm in CT.

If this non-response keeps up into the spring I just might HAVE to buy one over the internet.

Mongo