It could be both, depends on your specifications on how you put your venture with but definitely I would go to BTC hence this is the buy zone of bitcoin right now due to bad market sentiments. Some altcoins are worth it too, any top 10 on CMC is nice to buy and hold too.
Bitcoin will always be my choice no matter what altcoin may bring me , but of course if we can diversify then why need to choose one? i am for diversification as I am holding altcoins(with best potential of course) than pure bitcoin or pure altcoin , as remember never put your eggs in single basket.
I recently made some money through Amazon Kindle Direct Publishing, and I'm considering using it to purchase some Bitcoin. Only a tiny sum, roughly $800, is involved. What do you suggest doing right now? Purchase some Bitcoin or another cryptocurrency with a promising future.
What replacement coins would you recommend?
If you hodl your money 2 to 5+ years than go for Bitcoin, Because Bitcoin is best option for long term investment without any doubt.
For short term invest go for altcoin like Matic,Tron,BNB etc.
practical way , buy bitcoin for long term and altcoin if short term.