Quick background: I've been lifting for maybe a little over a year now, have made great progress. I'm 5'7" and started at about 175lbs body weight. I've since slimmed down to about 157lbs and have made progress on my big three (just met my summer goals of 200 on all three lifts, hit 205 on the bench press yesterday!!) but wanted to start getting in a better routine.

I had primarily done full body every time I went to the gym (every other day, not super strict, would sometimes skip a day), and would do a combination of barbell, dumbbell, and machine lifts. I've since made the move to pretty much only barbell lifts but was wondering if it was worth my while to start dumbbell lifts in some cases to work the stabilizer muscles more. For example the standing dumbbell shoulder press seems much harder than the barbell OHP, especially on my core (which I like). Is there any particular reason to prefer barbell over dumbbell if I can do both of the lifts? Are there any dumbbell lifts that are "better" (and I know that is a vague, loaded term) than similar or equivalent barbell lifts?

TL;DR - When do dumbbell lifts make more sense than barbell? Are there any instances where dumbbell are preferred or better?

Thanks!