Apples and oranges. AK-47 is fully automatic whereas AR-15 is semiautomatic.
Not exactly.
The original AR-15s -- including the ones Stoner/Armalite built to market to the US military -- were select-fire.
They all were stamped AR-15 until they began being manufactured specifically for the military. We had SpecOps/SpecWar troops in Vietnam carrying select-fire AR-15s before the M-16 became the general issue infantry rifle.
And there are semi-auto-only sporting arms sold today trademarked as AK-47s.
But, in fact, virtually all of the AK-pattern weapons manufactured since 1959, regardless whether they're semi-auto or select-fire, aren't AK-47s, they're AKMs. In other words, if you're less than 70 years of age, most everything you've ever called an AK-47 wasn't.