In order to use lbtc you have to swap out your btc (send it to some address and get lbtc back for it), you lose ownership of your btc

In order to use lightning you lock your btc in a channel and send it back and forward offchain as much as you like with almost zero fees, once you're finished you close the channel and publish final "account statement" of the channel to btc blockchain, without ever giving up ownership of your btc