I don't think any reasonable description would please Mrs. Bennet anyway; since in her heart of hearts she wants answers to questions such as:
How much is he worth? What is he looking for in a wife? When is he looking to get married? Is he one to propose quickly? Which daughter has the best chance? What should she wear/do/say etc. to win his approval? Do you have any information that will give us an edge? A basic physical description is probably welcome- but she would be most pleased with the nitty gritty!