Well, I want an opinion too, so I'm answering as well. 'Xcuse me. ;)
I'm gonna assume you're gonna use this as a Party Pokemon, so I'll cover everything.
Firstly, the stat spread is mentioned below, and it's all pretty even so if you want a good fossil Pokemon do what you please - but if you're gonna evolve it (which I assume you will) then I'd choose Tyrunt, as it has an incredibly high Attack and Defense stat when it's Tyrantrum. On the contrary, however, it's special stats are terrible.
Aurorus is completely vice versa, however, with having mediocre normal stats, and good special stats. So, I guess it depends on what you want. Aurorus also has a high HP stat, if you wish. But really, Tyrantrum just seems so much better.
Now, onto type weaknesses, people are definitely highlighting the fact that Aurorus has a terrible typing. Tyrunt and Tyrantrum has 5 weaknesses and 4 resistances, while Amaura and Aurorus 6 weaknesses (2 4x weaknesses) and 4 resistances. So, Tyrantrum easily wins this battle.
An even bigger disadvantage for Amaura and Aurorus is that most Fighting-type moves are physical, and since Aurorus have quite bad normal Defense, there's a bit of trouble there.
Plus, Tyrantrum is Dragon-type. 'Nuff said.
Now, I do want to show a good side to Aurorus, and that is how it does when it goes through the gyms. And even then, it's just as good as Tyrantrum.
Shalour City Gym - Fighting
-2 to -1
Coumarine City Gym - Grass
-3 to -1
Lumiose City Gym - Electric
-3 to 0
Okay, I just want to say now that I feel very sorry for Aurorus, and how many disadvantages it has throughout the game. It's nearly a deadly option to choose this Pokemon over Tyrantrum.
Laverre City Gym - Fairy
-3 to -1
Anistar City Gym - Psychic
-3 to -1
Snowbelle City Gym - Ice
-2 to -2
Yeah... choose Tyrantrum/Tyrunt.
Hope I helped...
(Why did I choose Amaura? >.<)
Sources: Multiple parts of Bulbapedia and Serebii