a) it is the one and only official wallet. All the other wallets are third-party developers. And for as much as everyone says that they are trustworthy I'd rather go straight to the official developers.
There is no 'official' wallet. Each wallet is a 3rd party wallet.
The real 'official' wallet would theoretically be the last version satoshi uploaded.
The developer of core are not the 'official' developer of bitcoin. Bitcoin is an open source protocol.
Why would you not recommend it then?
- It takes long to initially sync the blockchain
- It needs a lot of HD space (if pruning: the problem of rescan/reindex as HCP mentioned)
- After a few weeks without usage: syncing again
There are quite some reasons why people (especially newcomers to btc who don't directly want to contribute to the network) could choose
a better option than core as main wallet.