So what is a valuable selling point for Aggron then? Aggrons Rock Head ability or his worthless speed? His 150 BP move or its only 80% accuracy(which is as much as Stone Egde, what is a move that likes to miss)?
I don't really get the hype around Aggron. It is slow as hell and will only be dangerous if it gets off a Rock Polish. Even then priority can handle him quite well.
Let's see:
-10 resistances, of which 1 is an immunity(useful for switching into Blissey, and Toxic Spikes, but nothing special), but the important resistances he has are ice, rock, dragon, and dark, all of which are particularly threatening in the OU metagame
-150 BP(225 after STAB) physical rock move(excellent typing), only drawback being 80% accuracy and PP(Stone Edge is still one of the most used moves despite this flaw).
-Rock typing grants it a special defense boost in sand, allowing him to have 344 HP / 397 Def / 360 SpD, quite impressive for something with the palette of resistances that Aggron has.
-110 base attack allows him to 1-2HKO the majority of pokemon that don't resist it, even walls.
-Support moves like Roar, Thunder Wave, Toxic, Magnet Rise, and Stealth Rock, all of which are particularly useful for the current OU metagame
-His counters rely on either Choice Scarf(for Rock Polish) or are grounded, meaning a simple Toxic Spiker or bulky grass type handles the majority of his counters
-I probably forgot something, other than his defense, which I should atleast mention is 396 without investment