The reason why a company would want a good Reputation Quotient (RQ) is simple. A company with a good RQ is more likely to be successful. It is more likely to be able to sell a lot of its products and it is more likely to be able to attract investors.
A good RQ indicates that a company is strong in a variety of ways. It indicates that the firm makes good products. It indicates that the firm has brands that are appealing to consumers. It indicates that the firm has a good workplace environment. If a firm has all of these things (and a few others), both consumers and investors will be attracted to it. Consumers will want to buy from the company because of the quality of its products. Investors will want to invest because the company has a strong financial outlook. If the firm gets more customers and more investors, it will be more successful. A good RQ can help it to achieve these things. Therefore, a good RQ is clearly a beneficial thing.
Before answering the second part of your question, it is necessary to point out that a firm can have a high RQ without necessarily having the greatest of ethics. Ethics is only one part of an overall RQ. That said, I would prefer to work for a company with good ethics. There are two main reasons for this. First, I would believe that the company is more likely to succeed because it will not do things like breaking the law. Second, and perhaps more importantly, I would feel better about working for such a firm. I would feel that I was a part of a firm that I could be proud to work for. This would be very important for my overall job satisfaction.