An advantage of recruitment from outside the company is ?

(c) that it brings in new experience and skills to the firm.
I don't agree to the other 3 points: - it is not cheaper; new hire cost more and candidates join with the current market rates - definitely it will need to advertise the post to attract new talents - it will not raise jealously among the employees if you promote the talented and competent employee.
It will increase the motivational level and competition among the employees; especially if they see that others get fruitful outcome of their good performance.