For me, a Home Run referral for a banker is a business owner looking for a new banking relationship, a line of credit, or financing for growth. There is a clear need and a good opportunity to earn their business.
A Grand Slam referral is a business owner who is unhappy with their current bank, needs multiple banking solutions, and is open to moving the entire relationship. That could include business checking, treasury services, lending, merchant services, and personal banking relationships.
The difference is the depth of the relationship. A Home Run is a good opportunity. A Grand Slam is a long-term relationship where the banker becomes a trusted advisor and supports the growth of both the business and the owner.