I've used MySQL extensively for personal projects (all of mine have been at a pretty small scale). I've also used both Oracle and SQL Server for projects at large companies.
There's probably not much of an advantage in the database engine itself, but the SQL Server suite shined in 2 areas: analytics and reporting. The 2 add-on components made large-scale data mining & model-building much simple, and also automated the generation & delivery of complex reports tracking many metrics. I could probably do both with MySQL, but only with much more effort.
"I could probably do both with MySQL, but only with much more effort."
I know you could. You know you could. Most of the people here know you could.
But your boss doesn't want to bet on you. That would require him to manage you. Easier to spend a bunch of money through a capital expenditure request to get a piece of commercial software that already does it. When your boss(es) don't get the job done, it's easier to blame a vendor than an employee.
Or maybe said boss would spend less just buying software than paying an employee to duplicate an maintain the functionality. For a large enough company, one software license is not that big of an expense.
There's probably not much of an advantage in the database engine itself, but the SQL Server suite shined in 2 areas: analytics and reporting. The 2 add-on components made large-scale data mining & model-building much simple, and also automated the generation & delivery of complex reports tracking many metrics. I could probably do both with MySQL, but only with much more effort.