They both have prospects and basically for 2 different purposes, but asides so many things that makes bitcoin better, the fact that it has been able to stand the test of time, thrived no matter what and has a huge support Base, then I will always choose Bitcoin as No. 1.
ETH is nothing compared to bitcoin, I admit that ethereum smart contact was a brilliant idea but still this project has a lot of loop holes on their security. Every month there are always hacking event that cause for the value crash. Bitcoin is the mot secured and a lot of potential of all cryptocurrency.