In my opinion, bitcoin is more worth to buy. First of all, It has a more steady market than the altcoin. Although, it is much expensive than the altcoin, I would say bitcoin gives more confidence to the investors.
Yes, BTC is the safest buying now but the profit that we can have from it will smaller than altcoin. I think altcoin is safe enough to invest. If lucky, altcoin can give us 10 times profit or more while BTC is really hard to get 3 - 4 times