Long time ago when I was using it I preferred Gentoo because of ergonomics and better exposition to supply chain.

Slackware was very manual and some bits were drowned in its low level and long command chains. Gentoo felt easy but highlighted dependencies with a hard cost associated with compilation times.

Being a newb back then I enjoyed user friendliness with access to the machinery beneath. Satisfaction of a 1s boot time speedu, a result of 48h+ compilation, was unparalleled, too ;)