Despite being raised Conservative, it has been my impression that the only conversion that "counts" is an Orthodox one. I suspect this is the case for making aliyah, but under what other circumstances would the validity of one's conversion be called into question? What is the benefit of converting under one denomination or another? If one pursued a Conservative or Reform conversion, would her future children be at a disadvantage in any situation?
EDIT: Thank you, all, for your thoughtful and thorough responses! To me, it is telling that many intuitively picked up on the fact that this question pertains to a family member's interest in marrying a gentile woman. If anyone has further insights, please continue. Thanks.