Both have their place and it depends on what you want the lifetime ISA for and your time horizon.
e.g. if you’re using it on a first home in the next few years - cash is probably the better choice as a S&S ISA risks being down when you need the money for a deposit.
if this is just for retirement and you’re using the LISA to get the government bonus - a stocks and shares Lisa is better as it will on average return more over the long term and protects against inflation
Thanks,
Luke