The most important quality of a sword (assuming unarmored combat)is speed. The faster swordsman almost always wins. This means swords MUST be light and well balanced. While a cluncky knife feels dead, a cluncky sword is the death of its wielder. Beware of swordmakers who think a sword is just a big knife.
In order for a sword to be made light, the blade must be both thin and tough at the same time. This leaves little room for luxuries like edgeholding and stain-resistance. What you need is a very tough steel and an appropriet heat-treat for it. Nothing else really matters.
Edgeholding is NOT important in swords. Swords are not used to cut manila rope, they are used to cut people and you will not need to do that very often. Stain-resistance is nice, but it compromises strength, which is unacceptable.
5160 is the standard all others are judged by. I don't believe you will find any complaints from owners of a well-made sword of 5160. This steel was developed for the auto-industry and is one of the most prolific steels produced.
The only real problem with 5160 is that there are several grades and stock quality varies from factory to factory. Stick with proven makers and you'll be okay.
6150 is potentially slightly better. But it is not as easy to find in the right size as 5160, so fewer makers have experience with them. As great as the material is, if the maker is not familiar with it, it's useless.
S-7 is the air-hardening variant of its superior oil-hardening brother, S-5. The Shock steels have a very good reputation but they are quite expensive in sword sizes.
CPM-3V is a newcomer, it's worth is yet to be proven for swords. While much tougher than steels like A-2, D-2, ATS-34, it is not necessarily on the same level as the spring and shock steels in terms of toughness. It does have advantages in edgeholding and stain-resistance. But these are attributes more for knives than swords.
A-9, never heard of it, sounds like another air-hardening steel.
It speaks well for the performance of 5160 that few makers feel inclined to upgrade, unlike knifemakers who use ATS-34. A lot of steels are considered "tough" by knifemakers. But tougher than what? Than A-2, sure. Tougher than 5160? I have yet to see it proven.
I would recommend you look into a maker who use 5160, 6150, or S-5 AND have a good reputation on knowing how to do a good job with them.
