Last year I asked the numbers to our IT department for a similar discussion.
On about 2000 macbooks, 2000 thinkbooks and 6000 hp elitebooks, all of various generations, the macbooks scored best on reliability and best on 'how many tickets do these users create for our service desk'.
The cost savings are there. But obviously there was still a significant amount of issues with these laptops. They are not perfect, but they performed better than the other two families.
The big issue with macbooks is usually that if they fail after 3 years, they are an immediate write off. The others get repaired. Oh and those butterfly keyboard years were horrible and nearly stopped us from allowing macbooks apparently.