For triceps growth
For triceps growth, the two are close. Overhead dumbbell extension rates slightly higher: more stretch, more of the work on the triceps.
Seated dip machine is easier to progress.
Both are good choices, and they train the triceps differently. Using both across your week covers more of the muscle than either alone: in studies, varied exercises grew parts of a muscle that one exercise missed. (Fonseca et al., 2014; Costa et al., 2021)
The research score comes from these, scored by hand from the studies. Lifter scores appear once an exercise has 10 ratings. How scores work
Overhead Dumbbell Extension. Same overhead advantage, harder to load and to get into position.
Seated Dip Machine. Heavy triceps pressing on a stable machine, without the shoulder stress of bodyweight dips.
For triceps growth, the two are close. Overhead dumbbell extension rates slightly higher: more stretch, more of the work on the triceps. Seated dip machine is easier to progress. Both are good choices, and they train the triceps differently. Using both across your week covers more of the muscle than either alone: in studies, varied exercises grew parts of a muscle that one exercise missed.
About the same: both are easy to learn.
Overhead dumbbell extension needs dumbbells, so a home gym covers it. Seated dip machine needs a machine, so for most people it’s a gym exercise.
Seated dip machine: it rates Excellent for joint and recovery cost in our research rubric, against Good for overhead dumbbell extension.