Hi Kiko,
In standard you don't have any tcode to compare and post you the results. You need to develop your own report with required logic. CS14 BOM cmparision is available provided material number should be given as input.
Fetch all the FG's Materials specific to plant from tables MARA and MARC
Use FM CS_BOM_EXPL_MAT_V2 to fetch the BOM components for each FG.
Write logic to compare the BOM Components with respect to component material number and qty
Thanks & Regards,
Ramagiri