Treat sponsorship as a financial package tied to a career commitment, not as free tuition. The value is substantial, but part of that value is compensation for giving the firm a high probability that you return.
Start with the exact terms: what costs are covered, how long you must return, what happens if you leave early, and what repayment obligations apply. The consulting-firm MBA sponsorship guide explains the common structure.
The decision depends on how uncertain you are about your post-MBA path. If you already expect to return to consulting, sponsorship can be extremely attractive. If the MBA is primarily a pivot opportunity, the commitment has a real option cost.
Compare the after-tax value of the sponsorship with the flexibility you are giving up. Then decide whether you would still choose the same MBA and return path if the tuition benefit were smaller.