Gnosis encourages doubling down on your position and then you win.
Augur is not like this because it is fairly expensive to contest a result you think is wrong. Contesting a result on Augur requires the entire ecosystem to take a vote (i.e. do work) to ascertain what is true rather than leaving it up to a few people to keep doubling down on their position. They get paid for that work either from your bond posted to contest the result or by removing stake from liar reporters.
If however you pay the cost of contesting a result and you are right then you get that cost back and the stakeholders in the ecosystem who reported wrongly are punished. After all it is the job of reporters to identify the truth. Bad reporters are punished by removing and reassigning their stake to those who are more willing to report truthfully.
In this way the reporting system purifies itself from bad actors.
I don’t see the same incentive architecture operating here. Instead I see an incentive architecture which says “ok if you are bad you’d better be prepared to be really bad or else don’t even try.”
But even if there were bad actors in the REP community it could never spill over into ETH because the ultimate oracle splits the REP token into two different tokens such as:
REP Trump won
REP Hillary won
And this limits the impact to only the community of people who actually care about the outcome of this market namely REP holders. This is the benefit of an ultimate oracle trading REP instead of trading on ETH.
In Augur the ultimate oracle is not money at all but stake in the system which would be destroyed by bad actors attempting to game it thus no one should game the system because in successfully doing so they are destroying the value of the token (Stake) they are attempting to capture.