Ripple has been smart about iterating their product over and over with banks and regulators alike. On their board that have economists, former financial regulators, lawyers, former members of the NY fed, former members of PayPal, etc. This means that they are coming up with solutions that a) solve real problems that banks have and b) are compliant with financial regulations out of the box. The problem they have identified is one of real-time settlement especially in cross-border remittances. This use case stands to reduce remittance fees and free up capital that was previously stored in correspondent bank accounts. The technology stands to dramatically reduce international remittance fees. Ripple is building technology that doesn't require that banks or individuals use XRP in order to use the real-time technology. So, why would anyone want XRP then? 1) Well, their technology allows one currency to be immediately converted into another currency. For rare or medium-interest currency exchanges some time multiple currency exchanges are required to exchange one currency for another which means that the sender pays multiple FX spreads. XRP stands as a bridge currency to provide a near-shortest FX path. That is any currency can be converted into XRP and then into the currency of choice thereby lowering the number of spreads for most currency exchanges. 2) If XRP is liquid to any currency then the universal value of XRP will be highly stable. If you store you money as XRP then you're sheltered for big swings in the price of any particular country's currency. If you live in China but have your money in XRP then China devaluing it's currency doesn't negatively affect you. Ripple just inked a deal with SBI Holdings that will likely see XRP offered on trading platforms, the price will likely go up. But nothing is definite so speculators beware. Ripple is 100% premined and Ripple still holds 65% of all XRP. They can manipulate the market at will but there's no evidence they've done so to date.
Ethereum is not in competition with Ripple at all. Ether is the currency used to pay for computational work within and secure the Ethereum network. Ether only has utility within the Etherum network so you're speculating that Ethereum will be the dominant network for smart contracts. Ripple abandoned its smart contract platform Codius so they're not in competition on this front. BitCoin doesn't have a native smart contract platform. Ethereum is making a lot of progress in terms of smart contracts but they don't have any commercial products in active use yet and likely their platform will not be optimized for all types of smart contracts so it's unlikely they'll control the majority of the smart contract market. In all likelihood you'll see other smart contract platforms emerge that address specific use cases that Ethereum is not well-suited to address.
BitCoin is the original. Supporters of bitcoiners tend to be philosophically dedicated to the digital asset. We say it's decentralized but not much more so than Ripple (and Ripple is quickly decentralizing). How many miners control the network? Bitcoin will never make as much sense for point of sale usage as XRP or Fiat to me because of the confirmation lag time in the network. Sure, some transactions can still be processed off chain and batched but this creates counterparty risk as not all transactions will be honored. Risk increases fees. I do think that BitCoin has a future in terms of functioning not as a digital currency but as digital gold. People will see it as a safe, decentralized, uncontrolled, anonymous store of value. You'll see the value of BitCoin rise and fall inverse to faith in the global economy or national economies (as we recently saw with China).
The argument as to which is the best or which will be the dominant currency is not a useful argument in my mind because they address difference use cases. If you're philosophically committed to decentralization and anonymity then stick with BitCoin because identity controls will exist both within Ethereum and Ripple. If you're just speculating then diversify your portfolio and hold all three currencies in proportion to faith of the success of each. Personally I hold XRP and BitCoin right now and will get into Ether once the price comes down a bit to try to catch it before the next wave up. But it's all speculation.
Very well said cmbartley