Hi, We have a lot of kids in the neighborhood going to both these schools. As per their opinion, I think BVM is better than PSBB for CBSE. However these schools start from Pre KG and may not have (or have very few) openings for LKG and that may be closed already too. Kindly contact the schools and you may want to meet them and discuss.
Also look at other schools for options as both the schools are in high demand. Another option could be that you put your kid in a small nursery school for LKG and try for admission for UKG in all these big schools. Just my thoughts. Thanks.