There's a problem with what you're asking, and that's a definition of "efficiency".
As a weapon of war, the sword is almost completely obsolete. For this reason, little comes in serious advances of sword technology, other than occasional trickle-downs from other material technologies.
For this reason, there's little to judge how efficient a sword truly is, because the sword's context is no longer around in a way to be truly proven. The same goes for people who come up with "new" styles of swordsmanship(usually teenagers playing in their backyard, but not always...). They cannot develope a proven system because they aren't exposed to the combat that the system is supposedly designed from/for.
The only applicable efficiency I can see is cost vs. quality. At the very least, swords are still testable through target cutting.
Now, the only modernized swords I can think of are generally the "tacti-cool" designs. These are no more effective than similar designs of the past, but they use modern materials, and of course have black blade-coatings.
Of these, the prominent ones in my mind are:
The Angus Trim tactical sword line.
Criswell tactical Katana.
John Gage tactical gladius.
American Kami swords.
The Warren Thomas Katana.
There are also plenty of mass-produced GARBAGE marketed as tactical swords, but I won't count these.
When it comes to cost/quality ratio, Angus Trim probably wins. His regular sword line is known for being great cutters, and very well balanced for practitioners. This experience went directly into his tactical line, so they are definitely build as swords(as oppose to just big knives with crap balance). His swords, I believe, are the cheapest out of the list, and he has a decent lineup of different models to choose from. They might not be the ABSOLUTE best, but that all depends how much one truly wants to spend.
The biggest joke, I have to say, is the Warren Thomas Katana. I'll admit, he was really thinking outside the box, but the overall product is something I'd steer clear from. The entire sword is made from carbon fiber. The blase is carbon fiber sandwiched around a piece of Titanium that forms a ~1/4" wide cutting edge.
Probably looks astounding to people who don't understand swords, but the size to weight ratio is probably crap. People seem to be generally convinced that the lighter a sword is, somehow it's suddenly better. Alas, you can only lighten a sword so far before you lose the ability to propel its mass through the target.
Not to mention the crap edge-retention of Titanium.
I'm convinced that the only way to use Titanium in a sword-blade is to have it blast-welded to a steel cutting-edge. Of course, the cost of doing this would FAR FAR FAR outweigh any gains in performance.
