I was curious about this too and asked one of my Korean co-workers. I believe that it's correct that 부엌 is "genuine" Korean while 주방 is sino-korean. My co-worker explained it to me like this; 부엌 refers to a kind of traditional Korean kitchen with an 아궁이 (type of traditional Korean stove heated by burning wood), you would probably not eat in a 부엌 but there would be cooking supplies and things like 된장, 간장, salt, flour, etc. 주방 would be somewhere that would have maybe a gas stove and could include a dining area like you might find in a modern apartment. However, the older generation would be more likely to use 부엌 while the younger generations are likely to maybe not know the difference or use 주방 more often. In modern usage there isn't really a difference in meaning but if you look at the history of the two words that's what it is. (I was explained this in Korean and my Korean is far from fluent so this might not be a perfect explanation).