There was a thread some months ago "Thoughts on stick for city walking, possible defense..." that ended up getting rather nasty. There was a fellow who went by "Nameless" whose main objection was that if you are feeble enough to feel the need for a stick, the use of one will probably be ineffective, if not worse, because an assailant could just grab it away.
I'm not certain that is quite correct, but I must admit that I have enough joint problems, grip being one, that I would be hesitant to engage in a fight.
But here is what I can offer.
Decades ago, when I was training in martial arts, I learned something very useful, the hard way. There is a minimum radius that one must maintain. For younger folks, there is about a 3/4 second lag in response. What this means is that if one is close enough that a blow can be struck in that time, the hit will come before there is any consciousness of it coming in. What I learned the hard way was that sparing w. a fellow of almost the same age and size, he could kick me in the head before I could effectively block him.
To apply this to a fighting stick, longer is better. A jabbing motion to keep the attacker as far away as possible buys time.
The length of the stick also increases the angular momentum. Pre conquest shillelagh were long enough to be fatal. Later, adding a lead weight compensated for legal shorter lengths.
If one looks at a Chinese bo staff, they tend to be 5 - 6 feet long, and made from a wood that flexes without snapping. The best No. Am wood appears to be hickory, far and away. Very hard, and very resistant to snapping from sideways force. Reasonable light.
When I was practicing martial arts, a superior belt, who was ferociously strong, showed his father a manual on fighting w. a cane. His father had been using a cane for some years, and was comfortable with it. He was able to fend off attacks from his son, altho I always supposed it wasn't an all out battle.
That said, check out the British invention called "Baritsu." I suppose one should be able to match the range of motion shown, and be able to keep it up for a minute.
My opinion is that at present, even given the best stick, I can't muster enough skill to last more than a few blows. At best, I hope carrying a stick is at least a little daunting.
I suspect pepper spray might be more useful. An old union man suggested just carrying a big bar of soap in a sock. A good swing would knock anyone silly, leave no more than a bruise, and if questioned, the evidence was that one was just going to take a shower.