First, about the UV bulb Air Knight...a little study suggests that around a year usage is about right. I read about ballast problems, and the Carrier Infinity seems to count off the hours to recommend replacements. But, if very well could be worth $100 a year, depending on effectiveness. Since if it quits, the unit is not effected, it is an option that is truly optional.
Carrier controls: The Trane guy was a straight talker, and he said that the Carrier communicates better in my unit size range. He said the next step up commucates, but he ruled them out for me because he, upon knowing my status, single, no children, and low bills, said that they cannot pay out for me. Married, children, different story.
Cost comparison: It looks like the Trane will be close to $1000 cheaper. The Trane fellow didn't represent as well because my brother is his vet, and he had lots of stories about how my brother saved the day, etc, so it was hard to stay on topic. For pricing, he showed me a printed lamanated list from the manufacturer, and added around $200 to the price. The Trane guy said either choice, I can't go wrong, and if I buy Carrier, and something doesn't work out, give him a call, and he will straighten out the Carrier. (Essentially, no hard feelings, glad to help either way because when he was a kid, my brother used to help him with his pigs for little or nothing, and even as an adult, barely charges him anything.)
A buddy at work has Carrier, and highly recommends it. My brother, a different vet, has Trane, and highly recommends it.
It's a lot of money, which I would gladly pay if I knew it would give me good service, but enough of you guys have written to say that install is critical. I will take the day off on installation day, and hope that helps the install, rather than hurts. I don't know what an excellent HVAC man would know, but as a former plant engineer, I had to intervene with our large chillers some. These were really old Vilter units that were belt driven, and looked like electric motors driving V-8 engines. When I had to pick the replacement, I sweated that harder than my purchace for home, because people keep "score" of who bought what, and your name in a factory can be tarnished for years because you bought junk.
I know right from wrong, but having to guts to correct a craftsman is tough. They don't like it, none of them, including our craftsmen at work. Also, there is always the soul searching about is what you see as big a deal as you think it is, and are you TRULY right.
I am leaning toward Carrier because the saleman crawled under the house in cacky slacks and measured the whole thing out, and that impressed me. If the saleman were actually going to do the install, I'd be "in like Flynn" because I am convinced he knows his stuff, and is a stickler. But, perhaps, if I am lucky, that reflects on his entire organization. The Trane guy didn't do that, but that may not mean anything really, since he might have great crews who can deal with anything.