I don't see the difference. It's all payment for labor, negotiated at the beginning of employement as: "I do this, I get this." You can tack the word "bonus" on there, but it's not a gift, it's not just something the employee finds and keeps. It's part of compensation for labor performed. It's a different FORM (actual direct dollars, payment towards an insurance company on an employee's behalf, payment for classes on an employee's behalf) but why should that difference in FORM of compensation have any bearing on how we treat it?