Splicing allows wallets like Phoenix to show you a single balance and offering receive/send of both lightning and onchain with as small as possible fees.

Muun-like simplicity, while being non-custodial, having less fees and even more solid experience.

For node running, it provides much more flexibility for channel management. Channels can be grown and shrinked in a single transaction without need for closure.

TLDR: if you need a bigger channel that is already open, without closing and opening a new one, now you can expand it. Fees onchain involved anyways.

Phoenix is doing this splicing quite well.