For your abs
For your abs, decline sit-up rates higher on our research criteria: easier to progress.
Hanging knee raise is easier on the joints.
Both are good choices that train the abs the same way, so they swap freely. Rotating between them every few weeks is an easy way to vary your training.
The research score comes from these, scored by hand from the studies. Lifter scores appear once an exercise has 10 ratings. How scores work
For your abs, decline sit-up rates higher on our research criteria: easier to progress. Hanging knee raise is easier on the joints. Both are good choices that train the abs the same way, so they swap freely. Rotating between them every few weeks is an easy way to vary your training.
About the same: both are easy to learn.
Decline sit-up needs a bench, so a home gym covers it. Hanging knee raise needs a pull-up bar, so a home gym covers it.
Hanging knee raise: it rates Excellent for joint and recovery cost in our research rubric, against Strong for decline sit-up.