All of the currencies in the top 5-10 are promising in one form or another. The reasons why people choose to invest in a particular currency are varied. Some people base their investment on their own values, and pick something that seems "right" for them in terms of decentralization and etc. Other people invest diversely across the board with no interest in the physical realities of what a currency succeeding actually means for the future of commerce, and are more concerned with a profit margin. Some people, can find a balance between the two.. and choose to invest in what they see as being profitable without letting their emotional or morale implications get in their way. XRP is a good example, because it goes against the grain of "decentralization" which is more/less one of the biggest driving factors that surmounted in the creation of cryptocurrency in the first place. However, it's been backed by Google, and some of the largest banks in the world (many of which reside in commerce heavy and oil rich Saudia Arabia).. While it goes against the grain of what cryptocurrency was invented for, it is practical, provides a fast transaction, diverse in that ripple is coherent with other fiat currencies, and it appeals to that large percentage of the population that feels some sense of confidence knowing that banks are backing this. The majority of people aren't trendy or up to date on some of the obscure details as to how cryptocurrency works, and with XRP you have something that sounds more mainstream and legit as opposed to the bad rep Bitcoin got in its earlier days due to the Silk Road.
That said, I personally believe Bitcoin will continue to be the driving force behind all other digital currencies for some time to come. It has age, its matured its reputation, it's shown consistent growth and resilience. It literally jumped $500 the other day from 12 noon to 2 am EST. That was roughly 20%. The thing about bitcoin is it is so volatile, which can be great for the savy investor who knows when to hold, fold, and walk away. Then again, it also matters as to what scale your investing. If your pouring thousands of dollars in, sure it takes some precise knowledge about future developments with the coin and a lot of confidence. If your going slightly smaller scale, or the money is purely disposable.. You could almost assuredly invest in BTC.. sit.. and wait. Your bound to see some dramatic fluctuations, but as long as your keep your timeline appropiate, you should come out on top. My personal strategy for BTC at this time is long-term. I plan to invest a medium amount of my disposable money into it, and just wait for the 10 Year mark. That honestly not a long time, but.. With each passing year, consumer confidence only grows and the places where transactions are applicable only continue to grow as well. I really feel that by the time it hit the decade mark, it will truly be solidified and recognizable by the mojority of the modern civilized population.
That said, where BTC goes.. Litecoin is sure to follow. Think of it as the direct companion market. I think that the two compliment each other so well, and the pure existence of Litecoin only further solidifies Bitcoin, just from a psychological standpoint. I personally feel that XRP will take off, but there are plenty of people who would disagree with me. That's fine, and I respect their opinions. IMO, my confidence in the near future is in BTC, LTC, Ethereum, and XRP. All of which are near the top of most respectable markets trackers