First off, if you’re working with a prototype, I’d strongly recommend using urethane casting. This manufacturing process is much more suitable for low-volume production because it doesn’t come with the high setup costs associated with injection molding. Therefore, sticking with urethane casting until you’re certain you want to produce thousands of units is going to be your best bet.

Casting will also be excellent for fine surface details. However, you’ll need to carefully monitor dimensional accuracy as silicon molds can experience wear and deformation after around 30 units. Is your dimensional accuracy important due to a pressure fit or a waterproof seal, or are you more concerned about surface details? If you have a small production run (less than 20), I believe any measurement error would go unnoticed, and casting would still be the best way forward.