But LTT-Linus is 17 years younger and Canadian. O_O

The first one.

upgrade upgrades only installed packages, and only when it can do so without adding/removing other packages. dist-upgrade will do the same, plus upgrade packages that have dependency changes. If package A v1 depends on package B, but package A v2 depends on package C instead, using upgrade will keep your package A at v1, while dist-upgrade will install the new dependency and upgrade package A to v2.