Build Quality

• The XF 100-400 is heavier due to its more metal construction, while the XF 150-600 is lighter and easier to handle.

Operational Differences

• The XF 100-400 has an external zoom, which can lead to lens creep if not locked, while the XF 150-600 features an internal zoom that avoids this issue and offers smoother operation.
• The XF 150-600 includes programmable memory buttons for quick focus adjustments, a feature absent in the XF 100-400.

Image Quality

• Both lenses produce similar image quality, but the XF 150-600 may yield sharper images due to its ability to zoom in closer to subjects.

Teleconverter Use

• Both lenses can utilize teleconverters without degrading image quality, allowing for extended focal lengths.

Personal Recommendation

• If starting over, the speaker would choose the XF 150-600 and the XF 70-300 for a versatile setup, highlighting the advantages of the newer lens technology and features.