Okay, that is an interesting perk, where could I read about that and come to the same conclusion? For some reason I don't recall the white paper explicitly saying that but it wasn't comparing itself to cryptonote to begin with.
It's a property of the zero knowledge proofs in question; they're called Succint Non-interactive Arguments of Knowledge because their size grows sublinearly with the size of the statement being proved. In the case of ZCash, the statement consists of proving things about the blockchain, and things are set up in such a way that the size of the proof used is 288 bytes, ALWAYS.
Have you talked with the monero team on how they plan to address it?
They might not have a good answer (cheaper storage, computers faster in the future), maybe they do have some solutions in mind
This seems to be an issue with zcash too? Can you explain why it isn't?
Given current information if seems like these problems won't become apparent till the year 2021