I think you are making this over-complicated. Trojan has been the industry leader in the design & manufacturing of deep cycle batteries for over 50 years. When other brands want to establish their deep cycle battery legitimacy and quality, they compare themselves to Trojan. That's what is meant by the "gold standard". It doesn't necessarily mean they are actually better, but they are viewed as the hallmark of the deep cycle breed. Their factory is in Sante Fe Springs, CA.
Concorde/Lifeline is an industry leader in sealed batteries, which they supply to the aircraft industry. Their AGM deep cycles are highly regarded for quality and reliability, perhaps because of the airplane tie-in. Again, not necessarily better than any other, but they have the track record whereas others may not.
Not all Sam's Club stores stock all battery types and sizes, or the same prices. Here is the Sam's Club page for the 6v AGM in the GC2 (golf car) size. A couple of my local (central Florida) Sam's carry them @ $179.73, no doubt because golf cars are numerous there. Maybe not so easy to find in Wyoming.
https://www.samsclub.com/sams/duracell-agm-golf-car-battery-group-size-gc2agm/prod3870119.ip
East Penn, Exide, Johnson Controls and US Battery all make deep cycles and AGMs in both 6v and 12v and most common sizes. They are the factory source for nearly all domestic battery brands sold in the USA, including Interstate, Die Hard, Everstart, Deka and other popular brands. US Battery is particularly well-known as a source for moderately priced 6v GC2 flooded cell batteries and they now produce AGMs as well.
Vision is a large Chinese battery maker and a volume manufacturer of VRLA (sealed) batteries, including AGMs. I have no reason at all to doubt their products, so if you can get Vision brand AGMs in the size you want and a price you are willing to pay, go for it. I would be amazed if they are the only brand of golf cart AGM battery available in Tucson. However, given that golf cars use 6 or 8 6v batteries and AGMs are pricey, I suspect most places are focused on flooded cells, which manage to hold up well in golf car use. More people vote with their wallet than by choosing the top quality at any price.