Both Bitcoin and Altcoins are good investment. Its good to set aside funds for Bitcoin and Alts. If you have $1,000 to invest in Cryptos, I suggest set aside 60% to Altcoins and 40% to Bitcoin. You'll be surprised to see that your profits with investing in Alts are bigger than Bitcoin. There are times Altcoin price moves more than Bitcoins.
This is true, you need to look at the current market cap and with right call in certain moment you profit is much bigger then with bitcoin.
Some do same like you mentioned others are more focus on altcoin and profit then return to bitcoin, they have some amount that they want to exchange later.
Many focus on this type to invest bitcoin in large margin to some alt and when price starts to go down they sell.
There is no only 1 good thing. There is 2 options, actually 3:
1-Go with bitcoin only and if bitcoin breaks down new ATH values, be a rich guy.
2-Go all with alt coins, they're potentially making critic price movements.
3-Find a balance and have alt coins and bitcoin at the same time.