I think they care for each other equally, but I think that Dean is a bit more protective.

It's a close one. But Dean has almost this dependency, like he identifies himself as Sammy's older brother and protector (his little speech back in All Hell Breaks Loose, for example).

It's like because of his dad and the way he grew up, it was always his responsibility to care about Sam

it's non of the above reasons, its simply because dean actually LOVES his brother more than anyone or anything in this world, and Sam COULDN'T care LESS about dean.

^You really think that? I can think of loads of examples which prove otherwise.

Seriously?? Dean girls are really crazy. Dean physically and emotionally abuses Sam as he sees fit. As he said it, "this is a dictatorship". He manipulated Sam and let an angel violate Sam's body, and on this show possession is an obvious metaphor for rape/assault. Dean may care about Sam but most abusers do love their victims. "Being protective" is a really poor litmus test to gauge which character loves who more.

Sam actually respects Dean and all of his choices. Dean can't stand Sam being happy when the happiness doesn't have him in it. Dean's love feels almost conditional. That is not how love works. Y'all are treating a control freak's actions as loving just because you think he's hot.

^Sam Girl here.

The Gadreel possession was just one example in a long line of the brothers doing absolutely anything to save the other, even with the knowledge that the one being saved wouldn't want it. Examples of Sam doing this in return would include removing the Mark of Cain, opening hell-gates and trying to make deals with demons while Dean was in Hell, and arguably also the whole demon blood storyline back in season 4. This is basically the core of their relationship.

I do hate it when I see some of Dean's more fanatical fans criticising Sam's Dean-saving choices while praising Dean's equivalent choices though.