in my understanding, the significant difference is that the ETH token has uses other than as a speculation vehicle. XRPs only use case --besides flipping-- is by money transmitters (moneygram), who use it because ripple pays them in premined XRP to do so, but could and would conduct business otherwise if not for that subsidy. the southern district court of new york will likely find that ripple pays third parties to create an artificial usecase for its token and funds this by selling unregistered securities to a misinformed public. iow, it's a scam.
although the ethereum blockchain's main use has been to generate tokens that themselves have no use besides raising cash illegally as unregistered securities via ICOs, it is designed to deploy marketable distributed computation applications requiring use of the ETH token. unfortunately ethereum's useability is severly limited by its inability to scale. furthermore, the ETH token premine might have broken SEC regulations, and so might the blockchain's move to PoS. but i doubt ethereum gets hammered in court the way ripple is about to. rather ethereum will likely met its fate in the marketplace, where it will be found uncompetitive, as it is expensive, slow, and cannot incorporate significant adoption.
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