As far as I know only 6 confirmations are required for a transaction to be considered practically irreversible. Is it different for coinbase (reward) transactions?
Yeah, it's different for coinbase transactions because those transactions and the reward from them vanishes if that block is ever reorganized out of the main chain, whereas ordinary transactions will generally be included in the new chain too. It's as much a protection against technical issues as it is malicious attacks. I think there have been a small handful of reorganisations that are larger than 6 blocks in practice, and this has generally held up well.