If you use a single UTXO onchain to coinjoin, you cannot pass more sats than you have in that UTXO... Meanwhile through a single LN channel you can coinjoin as many sats you want. More than that, if you are smart you can make it to leave NO onchain trace.. Just think about, even if you are traced, a single UTXO of 1M sats that is in a public block, in fact it was transferring let's say 10 BTC through that single channel and nobody have any trace (except the channel peers - but that is another aspect).
Think in perspective. Mastering LN is an art of using all its properties and solutions.
If you use a single UTXO onchain to coinjoin, you cannot pass more sats than you have in that UTXO...
Meanwhile through a single LN channel you can coinjoin as many sats you want.
More than that, if you are smart you can make it to leave NO onchain trace..
Just think about, even if you are traced, a single UTXO of 1M sats that is in a public block, in fact it was transferring let's say 10 BTC through that single channel and nobody have any trace (except the channel peers - but that is another aspect).
Think in perspective. Mastering LN is an art of using all its properties and solutions.