MTBF of 2PC-strapped-to-quorum is no different from MTBF of a 2PC-strapped-to-spof replicas.

MTTR is bounded by reelection latency, rather than replica recovery, although you still may eat a write amplification cost for rereplication.

write amplification is 3-5x of non-quorum-backed 2PC system, depending on replication ensemble size.

google further multiplies write amplification with geo-redundancy, so bump that WA by another 3x+.

it's an insanely high cost to pay for availability, but for an advertising company it's important to count the beans accurately.