I don’t have any specific information on the difference between the Jenning’s bit series but I seem to remember that the lead screws (the point) came in single and double thread styles. The double thread lead screws had finer threads so that they were more suitable for hardwoods than softwoods. I have bits under several names ( even though I suspect that some of them were manufactured by the same people) and have discovered they all seem to work well if sharp. The Jennings bits do tend to clog on soft and wet woods because the double main threads are close enough that large chips will clog them up. The single screw Irwins just have more clearance for the chips. I prefer to buy older tools and restore them to use and bits are widely available. Whether the bits you are looking at are a “good buy” or not is something I can’t answer for you but the company does have a good reputation.
What I would really like to address is the osage orange pouring from your ears. I was warned as a child not to swallow seeds or they would grow inside me so I am wondering how the osage orange got started and if it causes you any problems. I am at that age where my hair has relocated from my head and has started to show up in places that many folks find unattractive, ears included, and as a result, trimming has become a regular activity. Hair is bad enough and I can’t imagine having to keep osage orange trimmed back. It is good that you are finding a use for it but it must be inconvenient to have to let it grow enough to make a mallet before you can trim it.