It is so, so hard not to compare children. After all, parenting is easier the second time around because you know what you are doing. You picked up that experience with your first child, so it is natural to take what you have learned and apply it to the second.
When that knowledge doesn't work you wonder what the difference is?
I have two girls and the similiarity ends there. Two very different pregnancies ended with two very different babies. The first a week late, nice and round and we had a horrid time learning to feed. The second, just over three weeks early, small and lean and took to feeding straight away. My second is about to turn a year old. She has just started saying 'mummum' today, is not crawling and eats a huge amount everyday. Her older sister was close to walking at this point, not talking and a good although increasingly fussy eater.
I don't go in much for quizzes but was taken by the 'Baby Whisperer' quiz designed to help you understand your baby's individual personality. My four year old was an angel baby (the kind most parents probably want, especially in the first year). They are no trouble, go to sleep when you want them to and wake up happy. On doing the quiz for my nearly one year old she comes out as 'spirited.' Spirited babies tend to wake up cranky/ crying, can get off track pretty quickly and are pretty good at making their needs known!
I did the quiz because I wondered if the approaches that I used with my oldest daughter were just not working with my second. My eldest daughter would be put down for a sleep, and just go to sleep. My youngest will end up sitting (then can't get back down) or end up stuck in a corner. To do this she bucks her body to get out of her safety sleep and then uses the bars to pull herself along the cot. I wish I had a closed circuit camera as it must be awesome to watch.
My oldest daughter would eat what she was given quite happily and passively by spoon feeding. My youngest likes to feed herself (but can't normally feed herself enough so needs a bit extra off the spoon).
Now I don't necessarily think that a quiz and a single approach will suit all children, but have found it a good reminder that some things that I thought were prettty universal with children (sleeping, eating) can need different approaches depending on the baby's personality.
I realise that what I have written isn't new or particularly revolutionary, but am interested to hear about other people and their experiences!