monero txs are slightly bigger in size than a btc tx, but a monero tx is smaller and more space efficient than a btc coinjoin so you end up paying less in fees and having less blockchain bloat for greater privacy, mining was solved with the creation of randomx in 2019 so no need to keep up, the State needs to control 51% of all CPUs that exist in people's houses, and also the creation and sale of new CPUs that enter the market very rapidly, versus controlling some big mining farms in a single place in BTC, or the creation and sale of ASICs which take months to develop and deliver