$BLZ in my opinion is a good project to hold long-term. It is backed by a working company offering decentralised, secure and highly scalable data storage for decentralised apps (Dapps).
Recently they partnered with Matic and Elrond to provide data storage for Dapps on both networks, which I think is an interesting move. $BLZ is important in the system, as it is needed for staking, payment of data storage service and payment for validators/node operators.
At the moment I cant find any cons, I give $BLZ 4 stars.