Aperture shows and edits the file you choose as the master. If the JPEG is the master, you’re seeing the camera’s already-processed version; if the RAW is the master, you’re seeing Aperture’s interpretation of the sensor data.

That’s why JPEG often looks better initially, especially in low light or high contrast: the camera has already applied processing such as white balance, contrast/tone adjustments, sharpening, and often noise reduction. A RAW file usually starts flatter and less polished because those decisions have not been fully applied yet.

RAW isn’t worse—it just needs more post-processing. The benefit is greater flexibility for adjusting exposure, white balance, highlights/shadows, and overall rendering.

In practice, use JPEG as master if you want a ready-to-use result with minimal editing. Use RAW as master if you want maximum editing latitude and are willing to process the image yourself.

You generally can’t precisely recover or inspect everything the camera did to create the JPEG, because that processing is proprietary and varies by camera settings. The practical approach is to use the JPEG as a visual reference, then add your own sharpening, noise reduction, white balance, and tonal adjustments to the RAW until it matches or improves on the JPEG.