NAH. You aren't the asshole for anything you've done, and I understand the bitterness of feeling like you work harder than an older sibling who gets coddled, but at the end of the day you don't get to parent your older brother. Working hard in school is wonderful, and your mom clearly felt you deserved to be rewarded for all the things you accomplished, but you should have some perspective there are many kids your age who don't get iphones for working hard in school.

You are updating to a new phone (I assume your mom is paying for this), and your old phone was paid for by your mom. It's not your phone to give. Besides, what do you plan on doing with your old phone if not give it to your brother? You've told your mom your opinion, but like you said, she's a hard working mother who likely loves both of her sons equally despite the 'accomplishments' of each. Sometimes its best to let these things go because it is likely putting more stress on your mom if you continue to make a big stink about it