I would choose both. Invest 50% to bitcoin and 50% to different altcoins - create a smart portfolio. Don't go all in, that's a big mistake. Diversify your investments.
It is wrong time to throw your 50% investment in altcoins. The market value of altcoins is contracting and we can see the same trend going on for some more time. Bitcoin dominance may cross 70% this month. So it is better to keep all money in BTC and wait for the moment. I think right time to go for altcoins is near Christmas. Trends show that prices of altcoins grow in holidays.