For buying: setting up a channel directly with a coordinator during times when network fees are low can help you buy sats during peak network times without the high fees. Doing the on chain option will be much more expensive in a high fee environment. Plus you’ll want a large enough purchase amount to make it worth getting that UTXO. With a dedicated lightning channel you can always be certain of finding a route for any purchase big or small as long as you have the inbound liquidity on your channel. Then you can move your accumulate sats to on chain when network fees are low again during a bear market.