@olli even if you dont need the varifocal it comes with an optical aperture thats nearly 2x the size of the fixed lens Starlights.. this results in much better photon gathering capabilities and that results in much better low light capabilities.
here's a F2.0 Fixed (3.6mm) Starlight:
here's the F1.4 Varifocal Starlight:
Both cameras had the exact same exposure settings, the only difference was the size of the aperture between the Varifocal and a Fixed Focal
IMHO, its worth the extra ~$35 for just the low light gains even if you dont care about varifocals..