Personally, I think it is better to exchange for BTC. If you take yesterday's example, BTC has grown by 15% again, which means if you transferred your altcoins to BTC. Now you have already earned 15%. I think all the same BTC is the best choice.
Many altcoins give more than 15% per day. Bitcoin is a more stable coin, which is invested without much risk, but the profit is not big. only in the long run.