So I've been rewatching Season 1 of SPN and I now realize exactly why I don't like Sam as much as I like Dean (not that I hate him!).

But Sam really acts like a spoiled child sometimes. As evidenced by his whole tantrum in Scarecrow. He gets in a tiffy because Dean obeys John without question. Dean trusts his father, I guess Sam doesn't. I can understand him being frustrated with John's mysteriousness.

But then he deliberately turns his back on a hunt where he knows for a fact that 2 people are going to die unless they do something. He does it to pursue his own personal vendetta/quest. Which is bad enough- but more than that he sets off with little hope of success. There's no way in hell he's going to find John from just a Sacramento area code. #1 That's not a lot of info. #2 John doesn't want to be found. #3 By the time he hitchhikes/buses his way there the trail will be ice cold.
So basically he was being a brat. IMO.

At least he came to his senses and realized that he should stick with the only family he's got.