I think IEOs that are lunched on big exchanges, tend to be better and have lesser risk, than those run by miniature or smaller exchanges.
If you are able to buy during the sales, it is better, but I you decide to buy after listing, then you must be more careful.
Perhaps it might sounds different that some IEO on big exchanges led to loss for investors such as IEO launched on bittrex, initially IEO launched on Binance had a huge dump before it was recently pumped, but nevertheless IEO on bigger exchanges had some Lil bit advantage