welcome-to-sunnydale:

“Same circumstances”…this isnt about Sam not wanting to save Dean , it’s absurd. It’s all about choices/free will and the way they love equally each other. Dean’s love for Sam is consuming and beautifully selfish , he needs Sam like he needs air , he lives for him and him only.

Sam’s love for Dean is more hidden and selfless , he would put Dean’s choices before him  even if it means being miserable or/and killing himself. 

They are both the embodiement of two powerful and extreme kinds of love , no middleground for the Winchesters codependancy.