They’re very different characters actually. They share great normals (Hiasko’s are longer than Shin’s in general, Shin’s are faster), but other than that have pretty different gameplans. I think Hisako is the better character (hits harder, less bad fights), but Shinsako is still very underexplored in all honesty, and is maybe the easier character to just pick up and play.
I don’t think any part of this is true 
Check out this thread for a goodly chunk of base Hisako play.
And if you’ve got any specific questions on Hisako, please feel free to tag me and ask away. I can help a bit with Shinsako as well, though I’m not the absolute best with her or anything.