It's hard to argue against any Saylor Beall, but at 5 HP I tend to prefer Champion. I have 2 Champion R-15 based air compressors.
The Champion does have an aluminum head with steel liners, but there are no head gaskets to blow and no special tools required to service the disc valves. It runs at 710-734 RPM at 5 HP. This design has been around since the 1920's-1940's. The R-15 weighs 125 pounds which is light enough I can pick it up myself. They offer the Advantage Series which is basically the most common purchased configuration of the R series and available to ship immediately. If you want any customization, then you just get the R series and they'll build it to order.
If you skip to 1:10 here's one running
. This sounds just like the 2 that I have.
The Saylor Beall is all cast iron, but requires some tools either from them, or home made, to deal with the disc valves. The 705 pump runs at 845 RPM and weighs 220 pounds. It is the most USA made compressor. I don't believe any of the castings are made off shore. They should be about the same price as the Champion.
Saylor Beall's run test
https://www.youtube.com/results?search_query=saylor+beall+5hp+run
The Curtis uses reed valves so any valve work would require the head to come apart. It runs at 900 RPM.
This is an online video I found for the Curtis
I get your objection to used IR.