The LN protocol always look for the cheaper and faster path, with min amount of hops. It also depends on which wallet you are using, it may has some service fees too, usually 1% especially if custodial... if not, your node must have good connectivity with other nodes, otherwise the payment path will be expensive.

i.e.: for bigger payments, in low fee season, an onchain payment could be cheaper than lightning due to the fact that not many nodes have big channels.