than or rather than

Best ---> rather than
better ---> than [because better is a comparative form
Which is correct?
I think it is best I hire someone else part time and keep him rather than hire someone else full time and fire him.
I think it is better I hire someone else part time and keep him [rather] than hire someone else full time and fire him.

It's best to do that rather than this.
It's better to do that rather than this.
It's better to do that than this.

It's best that we do that now rather than later.
It's better that we do that now rather than later.
It's better that we do that now than later.

Thank you