Both ETC and BTC have risen significantly in price this year (and have also fluctuated about a fair amount too) - although price can be a good indicator of strength it can be manipulated - and also crypto is so volatile that on any given day you could get a totally different picture (e.g. could be up/down 20% for whatever reason).

I don't think you can say one is "better" than the other becuase at the moment they're used for different things - Ethereum seems to be used for ICOs (so many ICOs!) and smart contracts for business automation, whereas BTC is more about payments etc...

I don't think either is going to go away any time soon, but that's just my two cents