Your value proposition is not your logo or your mission statement. Below are popular marketing terms and their definitions:
Strategic Planning and Value Proposition:

How they work together: Strategic Planning is your opportunity to step back from your daily operations to look at your organization today, and what needs to change in order to address strategic issue facing your members. The value proposition helps you focus on what members need the most.
As a real life example, an organization re-structured “networking events” to become “Connecting with like-minded people who are best at what they do (to build a meaningful network with other members).”
As a strategic goal, networking was never again mentioned; instead, mastermind groups and panels for distinct member segments were considered to help overcome significant changes in the market and the changes in the profession.
Vision:
Your destination; it is aspirational and usually aggressive; if you accomplish your strategic goals year in and year out, this is what the association or environment will look like at the end.
Mission:
Your purpose; why you exist, who you serve. Short, clear, and gives staff a roadmap to consider in their daily work.
Brand:
Your promise to members about how you will run your business over time. The brand guides decision-making around the board table. Your behavioral identity that helps establish a perception in the eyes of your members.
Logo:
This is the graphic depiction of your brand. It is your visual identity.
Value Proposition:
Your members’ rationale for choosing you, another association (or educational or news/information source) or none at all. This is not yours to decide, but rather you must discover it.
They all need to align, but none should not be the same.