I'm pretty new to this, and after researching a bit, I feel like ETH is going places and has far fewer barriers to expansion that BTC. I want to buy and hold some coins, and as of now i'm leaning towards ETH. but I can't ignore the fact that bitcoin seems like top dog still... so convince me to buy BTC instead of eth. Give a reason besides "first movers advantage" 
Why risk putting all your eggs in one basket? Invest in both. ETH's potential is definitely big, but I don't see it equalling BTCs price anytime soon. Depending on your capital, you might also want to consider investing in a few other top altcoins. The crypto market is too volatile, so diversification is key in any portfolio.