The benefit of investing in altcoin is to hope that you can gain more profit than bitcoin. As bitcoin has growth from $50 to $6000+, it would be very difficult to see bitcoin from here onwards to have another x10 in values. However, that is totally possible for the altcoins. Some of them only have marketcap of $10mil and if they manage to make it into the top coins, they can gain x10 or even x100.