shielded vs unshielded pros and cons?

Audio interconnects are generally carrying low-voltage signals which means any picked up interference, from unrelated sources but also from nearby cables, can significantly impact the signal fidelity.

I think all audio interconnects are shielded? There's a bunch of information on this topic if you search online. It's power cables and speaker cables that are usually unshielded.

"...I think all audio interconnects are shielded?..."

No they are not all shielded. A shielded cable can help reject noise if there is noise nearby. If you are in a low-noise environment and your system is not picking anything up, shielding is not required. 

Shielded cables have been an absolute necessity in my systems between SUT and phono pre. 

Other than cost, there is no downside to shielded cables.

There are vendors on ebay who are small-scale makers of ICs, who claim sonic differences between shielded and unshielded versions of what is otherwise the same cable.