Wait wait wait! Some things haven't been pointed out.
You want to have a Fighting type move to take out Ice types right? Ice and Rock probably....
Anyway! If you did the MATH, a super effective Brick Break isn't going to do much more than Dragonite's STAB moves, either Dragon CLAW which is 120 BP with STAB or OUTRAGE which is 180 with STAB. Therefore, a super effective Brick Break STILL isn't going to do as much damage as Outrage, and is only a wee bit more powerful than dragon claw. Now, I don't know about you, but I'm not going to chance killing an Ice type with a wee little brick break. I'm going to either want to skiddadle, (Ice hurts) or get a surefire kill. Therefore, SUPERPOWER is the way to go. It isn't just more powerful, it is WAY more powerful. A SE Superpower is going to be 240 as opposed to a measly 150. If you want your opponent to die, you're going to want to finish the job.