i could say IEO is more save if you compare it with ICO, but if you ask about profitable, it depend on the project itself, neither in IEO or ICO if the project failed, the result is loss for you.
I haven't seen any failed IEO projects so far, and there are a lot of failed ICO projects, so far it's better to participate in IEO projects
only few exchange are conducting an ieo and most of them are top exchanges like binance , kuckoin , houbi and others . that might be the reason on why you cant see failed projects but as soon as the ieo's became popular , many new exchange will also join the party and thats the time that you will now see failed ieo's but the guy above you is right that the profitability of an ieo will only depend on how good the exchange was .
Only a large market that guarantees more investment in the IEO will gain profits, in some small markets they also try to implement the IEO system on their platforms but there are only a few investors who invest.