"Augur" vs. "Oraclize" : What is the main difference? Can we say that "Augur" is a decentralized Oracle against "Oraclize" as a centralized model?
Full disclosure: Am an Oraclize employee, but also an Augur fan plus REP holder and so am striving for impartiality. 

And so to the question: Not really, no. 

Oraclize is a really cool oracle service: They are essentially a data transport layer who provide authenticity proofs that the requested data was retrieved and/or computed in exactly the manner the requester of the data asked for. 

They don't guarantee the veracity of the data itself, only that it was retrieved/computed in exactly the manner the requester asked for, via third party proofs. And it is these that make Oraclize trustless - you don't need to trust Oraclize, only the provider of the requested proof type. 

Better still, this third party nature also allows a requester to appraise the data they are requesting. If choosing say a TLSNotary proof, you're actually relying on an AWS instance, giving you a sense of how much it would cost an attacker to hack such a thing, and allowing you to judge whether your smart contract needs a higher fiscal guarantee or not. And if then you do need a higher guarantee, multiple proof types can be requested, further increasing the cost for an attacker to gain access to/alter the data you're requesting.

And so now to Augur, which is a really cool prediction market. Here, financial incentives drive the accurate reporting of external data by its users. So Augur are a data source themselves, and are decentralized to the tune of however much is at stake, monetarily, on a piece of data being correct. One draw back is the cost of creating such a market, and another is then the risk of that market not generating much traffic, reducing the likelihood of receiving said data as well as potentially reducing the guarantee of accuracy of said data. These risks are inherent to the model and are difficult to assuage. Nevertheless, Augur is a fascinating prospect. 

Incidentally, these two different modus operandi can in fact work synergistically - Oraclize can be used to retrieve results from an Augur prediction market, or Augur can use Oraclize to resolve a market - how's that for meta!