Easy kid or difficult kid...?

Kids are hard work- no doubt about it. Some are easier to deal with than others. As a teacher, I feel pretty confident in saying that some are downright hard work!S I wouldn't say Alex is hard work, but he has been much harder to deal with than Megan ever was. He isn't really naughty and he is definitely more polite than Megan, but his behaviour and personality are much more challenging than she has ever been. Perhaps I'm looking back on Megan through rose-coloured glasses...but I dont think so. She is almost 4 now, very independant and quite compliant. She was a pretty cruisy baby, slept well from a young age and was usually happy. Alex has never slept well and still doesn't. His independance is so random and he is incredibly stubborn. All the tactics that worked on Megan are useless on him. Lots of teacher strategies I use at work aren't any help either. Maybe it's the terrible twos that have just stretched on longer than I had thought. Maybe I'm not used to little boys. Maybe I'm just unfairly comparing a 2yr old to a 4 yr old and wondering why they aren't more similar. I've studied human development. I've read behaviour stuff and boy stuff. I know how the toddler brain works. Maybe when Megan was going through all of this I was just too distracted by a non-sleeping baby that I didn't notice!!