Value generation, Core competence, Your development

The potential of a job inside a company often depends on the value (revenue or profit) it generates for the company, and its criticality (core competence) to the company. If the BU job gets you closer to where the company makes money, or how it makes money, this is generally a good experience for you.

You may also want to consider your personal career direction, inside or outside the company. What skills do you learn from the BU job? Are you interested in learnig those skills? Do you plan to develop yourself in that direction in the future? For example, GE is known to develop good managers, and IBM is known to develop good sales people. Those are core strength of a company and something you may want to learn while in that company.

I won't pay too much attention to moving up the corporate ladder. Getting the right skills and experiences generally help you more in the long run.