Exercises that apply greater resistance at longer muscle lengths produce similar muscle hypertrophy compared to exercises that apply greater resistance at shorter muscle lengths when total training volume and intensity are held constant.

Study: Partial Range, Full Gains? The Effect of 8 Weeks of Partial Range of Motion Training at Long Muscle Lengths on Elbow Flexor Hypertrophy and Strength in Trained Individuals

When people lift weights using either a short or full arm movement—while doing the same total amount of work—their biceps grow about the same, no matter where the hardest part of the lift happens.

Study: Placing Greater Torque at Shorter or Longer Muscle Lengths? Effects of Cable vs. Barbell Preacher Curl Training on Muscular Strength and Hypertrophy in Young Adults

When people did arm curls with weights that were harder to lift when their arms were stretched out versus when they were bent, both groups ended up with the same amount of muscle growth — as long as they did the same number of reps and lifted similar total weights.

Study: The Effects of Long Muscle Length Isometric versus Full Range of Motion Isotonic Training on Regional Quadriceps Femoris Hypertrophy in Resistance-Trained Individuals.

When people lift weights with more resistance when their muscles are stretched out versus when they're bunched up, both ways build about the same amount of muscle—so long as they do the same total amount of work.

Study: Similar Regional Hypertrophy of the Elbow Flexor Muscles in Response to Low-Load Training With Vascular Occlusion at Short Versus Long Muscle Lengths

This study found that whether you do arm curls with your arm stretched out or bent, you still get about the same muscle growth as long as you do the same number of reps and effort. So, you can pick whichever position feels better — it won’t change your results much.