Good question. Here are a couple of equalities between Elizabeth and Darcy.
1. They seem to be equal in intelligence and wit. Elizabeth is an "accomplished" young lady, yet she does not brag about any of her talents. Darcy has a formal education, but he knows that Elizabeth can hold her own in a conversation with him or others of high intelligence.
2. They are equal in maturity. Darcy, from a young age, has had to care for his younger sister and a vast estate; so his maturity in comparison to Bingley's is much more advanced. Elizabeth, though she is not the oldest in her family, is certainly the most mature (many would argue that she is more mature than both her parents) and feels the weight of having to worry about her younger sisters' welfare and places in society.