For biceps growth
For biceps growth, the two are close. Spider curl rates slightly higher: more of the work on the biceps, easier to progress.
Cross-body hammer curl gives more stretch.
Both are good choices that train the biceps 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
Spider Curl. Hardest at the top, where the biceps is shortest.
For biceps growth, the two are close. Spider curl rates slightly higher: more of the work on the biceps, easier to progress. Cross-body hammer curl gives more stretch. Both are good choices that train the biceps 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.
Cross-body hammer curl needs dumbbells, so a home gym covers it. Spider curl needs dumbbells and a bench, so a home gym covers it.
About the same: both rate Excellent for joint and recovery cost in our research rubric.