Itachi's Susano'o's sword has the capability to seal anything it touches.
Nope its anything it PIERCES. If it seals away anything it touches, it would have sealed away the heads of Orochimaru's hydra technique once it made contact, but it merely severed the heads like a regular sword. It has to stab something in order to seal it.
As soon as Itachi's Susano'o starts the swordfight, one hit and the swords are gone. seal away the chakra tha makes up Madara's Suano'o.
And as for time, Itachi was able to create enough Susano'o to stop Kirin, which is a split-second strike from the heavens.
We don't even know how strong itachi's susanoo was to stop kirin. Kirin was high damaging, but it had a large area of effect meaning itachi wasn't hit by even half of the lightning. If itachi's susanoo had completely tanked kirin, the uchiha compound would not have been destroyed or even damaged. And all the other times that we have seen itachi use susanoo, it was never instand, it takes at least 3 pages for him to form a complete susanoo.
Madara can use the tech's, but Nagato has learned certain ways to use the tech's that make them even more dangerous (it's almost never about power, but how power is used.)
What are these certain ways? I don't see how having more experience using shinra tensei will make your shinra tensi more dangerous than someone elses shinra tensei. The techniques work in the exact same way as nagatos, the only difference is that madara's techniques are far more powerful.
Tell me one way how nagato would use any one of these:
- shinra tensei
- preta path
- asura realm
- human path
- naraka path
more effectively that madara.