Which is better purely in terms of placement, XLRI BM or HRM?

Although choosing a course just based on placement records is not a good idea, there are some insights you must know before deciding.

• Placement is for the first job which you might do for 2–3 years while your career will span for 30–35 years. You should choose what you feel you want to be doing.
• You must have heard that HR roles offer you better work-life balance but it might not be true in every case. It depends a lot on the company, your manager, and your role. If work-life balance is your criteria, you might feel a shock when you join a company. HR might not have business targets but you may face other pressures.
• Placements in any campus depend on your luck too. HR batch strength increase in XL might make the competition for the good roles a little higher because the number of HR roles is limited. BM batch is still divided amongst Fin/Mar/Ops camps giving them specific roles but the number of opportunities might be higher. 

All in all, placements won't secure your future in any way if you choose a field where you aren’t interested.