Same or different preschool for children?

I have 2 children. Currently, one is attending a preschool which school fees is quite costly but environment is good. My 2nd baby is entering PG level soon and I am hesitating whether to place her in same preschool together with her elder sister which means school fees will be more expensive, or place her in a less expensive preschool but will be separate from her sister. Just wondering are there parents with children attending different preschools or generally is same preschool? Not sure if it will be healthy to separate them. In dilemma, neee some advices please. Thanks a lot in advance.