A thrust from a narrow and pointy blade, such as found in a sword cane, will have no difficulty penetrating even balistic armor.
What do you mean by "you may only have one chance"(paraphrase)
I have a real hard time envisioning a scenario where you could womp somebody with a three foot long stick several times, but could only stab them once with a sliver of steel.
Unless you mean that most sword canes are poorly made these days and are unlikely to survive more than one thrust...
As to the sword cane being an obvious weapon and losing the advantage of suprise, that's an offense-thing. On the defense some guy is gonna come up and try to kick your ass, then you pull out the sword, womp him with the body, and run'em through. It wasn't a matter of suprise in the old days, it was a matter of discretion. To be armed, but without people with timid sensibilities having to look at your weapon.
One advantage everybody's missing that the sword cane has is that it gives you two weapons; the sword itself, and the body of the cane. Properly constructed, the cane body can both give and recieve blows. If your opponent isn't armed with a firearm, this can be a distinct advantage if you know how to use it.
A sword cane is not an unskilled weapon, like a stick can be. If you are intrested in combative use of a sword cane this can be done effectively, but if you just want something to womp over someone's head with minimal training, the stick is the way to go.
If you are looking for instructional information on how to wield a sword cane, check out the historical rapier manuals, several are available on the web, check out www.thehaca.com,
look for a link labeled "resources" or something like that. Rapier and dagger technique can be modified to work with cane sword and body. Then do some sparring and such. Or if you want to get real good, seek instruction in combative rapier play. HACA is a good waypoint to find the various instructors teaching this stuff out there. Check their links page.
If you want to get a sword cane made up, I reccomend a colichmarde style blade, cocobolo body. Go for a friction fitted handle, not the screw on type. Crooked or ball topped doesn't matter, though you're gonna want to make sure that have something in the way of a handle built in if you go with the ball. Otherwise you just end up holding the ball, which is no good really. You will want as much as 5 or 6 inches of handle if you go with the ball, because while it provides a secore pommel for an authorative withdrawl, it leaves something to be desired while executing the thrust, it's good to have a little extra handle between you and the blade. Which is another reason why I reccomend a colichmarde blade, not only is the triangular cross-section stiff and strong, but it's not sharpened like a knife so it's somewhat safer. This isn't really such a problem with a crooked handle, as the curvature aids in retention. Which is why some navajas could get away without having a finger gaurd.
The easiest way to get the cavity for the blade in the handle is to have it made in two halves, however the cavity is only carved in one half, the other merely is glued on top of it. This can be strong as long as it is securely reinforced with a metal tip and throat. You will want to give it a good coat of paint to make the seam disappear. A better, but more complicated route is to have a hole bored through a solid dowel, and the have inserts fabricated that slide in and glue on the sides of the cavity to make it conform to the dimensions of the blade. I suppose nowadays you could have resin poured in around a heavily waxed balde for a perfect fit instead. You still need the tip, like on any cane, but you can skip the throat, which will make it less obviously a weapon.
A thrid option, if you're going with the two halves aproach, is to hollow out both sides to accomedate a metal tube which will house the blade. Again, it must be fitted to the blade in one of the manners described above, or something similar to them, to prevent rattling. The advantage with this method is that it makes the cane body heavier, which will give it a more-powerful whomp, while at the same time making the cane stronger. You still want the throat though to keep the wooden halves to split apart. Because more surface area is in contact, the glue has more area to hold onto, and thusly makes for a stronger bond than the channel method.
The second method is strongest, followed closely by the third, and then the first.
Any are sufficient done properly, and the method you choose should depend on taste and your ability to bore a substantial and deep hole through the dowel. I suggest welding a drill bit to a length of cold rolled steel rod.
If you can't find a cocobolo dowel of sufficient diameter, and can't turn one on a lathe, you'll probably have to settle for non-tapered cane made from a pre-fab dowel. I reccomend one of the 4ft. diamondwood staffs sold at www.museumreplicas.com.
Don't trim it to length until you have succesfuly made the blade cavity, that way you will have some small margin for error. These staffs are 1-1/8 of an inch wide, which is sufficient for a .5" wide blade. Half an inch is enough to make a triangular cross-sectioned blade about 16 inches long.
If you are worried about the lethality of such a slim blade, think about wether or not you would like a half inch wide hole through your heart, liver, lungs or eye. Besides, any wider and it'd have problem going through a rib cage. Sorry! Just talking shop...
Oh yeah, if you're wondering, I've made three of these things in my life. The first was an utter failure, the second and third turned out well. They were made for a friend, who liked the first I gave her so much she wanted a second.
Pretty coll toys. Certainly have more style than a stick.