Deciding whether a plant needs repotting or just better light

My rubber plant has roots showing near the drainage holes, but the leaves are also leaning toward the window and new growth has slowed. I can't tell whether it needs a bigger pot or simply better light. The soil dries in about a week, and I don't see signs of root rot. I'm tempted to move it closer to the bright window for a month before disturbing the roots. What would convince you repotting is actually necessary?