You’d be getting the supply chain put together by the software author in either case. It’s common to do both badly, but if you care about doing it well, that’s easier with npm (e.g. shrinkwrap, as mentioned) and can be taken farther (the non-varying artifact thing).
replyNpm dependencies resolve at install time though, so some of the pinned versions may have changed ownership or otherwise been modified since the author pinned them. With the curl | bash solution you're getting a singular supply chain packaged by the author at release time.
replyWith curl|bash you are literally getting anything that happens to be in that script. These are frequently poorly constructed, so not check hashes or pin dependencies they install.
Even security companies (see trivy supply chain attack) get these badly wrong.
replyI'm not replying here to say one is better than than the other (npm has obviously had its share of problems) but rather to combat claims that curl|bash is somehow safer, it absolutely is not, in fact it's all the bad stuff about npm without the pretense of being potentially safe.