What's the difference? And why?

[amanbthakkar]

SimpleStorage ss = SimpleStorage(simpleStorageArray[_simpleStorageIndex]);
vs
SimpleStorage ss = simpleStorageArray[_simpleStorageIndex];

Both work the same. Is the first one just additional "typecasting" to make sure that the object created is of proper type? Of course as mentioned in the video, I am assuming that the array is of type "SimpleStorage".

[PatrickAlphaC]

You got it :)

This first one "returns" a SimpleStorage type.

simpleStorageArray[_simpleStorageIndex]

This next one says to cast whatever simpleStorageArray[_simpleStorageIndex] returns, to a SimpleStorage type, so it's redundant.

SimpleStorage(simpleStorageArray[_simpleStorageIndex])

It's totally not necessary to do the SimpleStorage(...) wrapping for this.