Each have their pros and cons.
While most people are still on 1080 monitors, the iMac has been 1440 since 2009. For the last year I've been looking at a 5k screen while everyone else is still debating 4k. In 5 years this screen will still be better that most.
For business I couldn't use anything else.
For gaming I couldn't use one.
For business they are probably cheaper in the long run. Far fewer hardware failures, far less down time.
Your time doesn't cost anything, but when a business computer breaks down, the cost of the parts is usually insignificant compared to the downtime of the employee, and the tech who has to come and fix it.
In addition, training is far quicker and there are far less calls to tech support.
Even companies like IBM are currently buying over 200,000 mac's. According to them, 5% of mac users will call tech support, compared to 40% of windows users.
And you'd assume an IBM employee knows how to use a computer. What about non tech businesses.