How strong...

[Zzz]

Six Paths Coffin Seal is a jutsu that seals the Juubi into one's own body. That is one way to gain Six Path's power. Aside from that, I don't remember any other special trait from it.

Don't know where it says that only his Susanoo increased in power.

My bad, I meant the Senjutsu gained by the seal.
The special trait is the strength, speed, durability.

Sasuke would have gained an increase in the ones stated above, but he simply stored the Bijuu chakra in the Susano'o.