It's hard to say really. I never really tried to understand much about Ethereum, because it doesn't really sound like it's a "currency", rather, it's sort of a "database" system prototype. I'm pretty sure Microsoft bought out Ethereum as a testing ground for their Azure platform. So, in a way, I'm just not that interested in Ethereum.
I don't want to sound like some kind of shill for an altcoin on here, because I hate when people use FUD to encourage people to buy some of their coin. But, I personally think the new coin on the block that holds a legitimate value compared to bitcoin would be Monero (XMR). They are sort of a fork off of DASH, in which they both use the "cryptonote" code. If you don't know much about the cryptonote system, it's basically a way to anonymize transactions on the blockchain through "ring signatures". Monero is different because of a group of active devs working together on the codebase... whereas DASH has become sort of stagnant with active development.
DASH is also pretty well known for being insta/ninjamined at the beginning, so that the very early adopters have an incredible amount of coins under their belt... Monero was a fairly launched coin, which makes it more appealing to other people who weren't the very first people to hear about it.
If you want to read more about cryptonotes... here's the white paper:
https://cryptonote.org/whitepaper.pdfAlso, here's what's being worked on Monero as of right now; which is Ring CT (way of anonymizing the actual amounts on the block chain) this is being worked on by Shen-Noether... someone in the monero research lab:
http://diyhpl.us/~bryan/papers2/bitcoin/Ring%20CT%20for%20Monero.pdfAgain, I really don't care if you guys get into it... I just really like it to help remain anonymous in my transactions, and not have everything publicly available on the blockchain. A cool tool I use, primarily for buying stuff in BTC, is using my XMR (monero) and using
https://xmr.to/ to pay any vendor who accepts bitcoins, and pay with xmr to help remain anonymous. It just converts how much XMR is worth at the current moment of purchase (in BTC) and pays the vendor in BTC.
Edit: I will have to say though, that it does propose fixes for a couple of the problems that Bitcoin is facing right now... 1) XMR has adaptive blocksizes to adjust accordingly to amount of transactions being done 2) Tail emission features, where the total amount of XMR is added on to in the future to incentivize mining in the future (should be 18 Million coins, and then keeps adding coins as need... where it will get closer and closer to 21 Million over time, but keeps decreasing rewards so it never really gets there).