The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Panasonic 25mm F1.4 II ASPH and the Sigma 19mm F2.8 DN for their suitability to various photography scenarios:
Size and Weight Comparison
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Sigma 19mm F2.8 DN weighs 140g, 31% (65g) lighter than the Panasonic 25mm F1.4 II ASPH's weight of 205g.
Below you can find the dimension and weight table of the Wideangle Prime Lenses in Micro Four Thirds Mount for size comparison purposes.
Wideangle Prime Lenses in Micro Four Thirds Mount for Size Comparison
Lens Mounts
Both the Panasonic 25mm F1.4 II ASPH and the Sigma 19mm F2.8 DN has the same Micro Four Thirds lens mount. Some of the latest released cameras that are compatible with the Micro Four Thirds lenses are OM System OM-5, Panasonic GH6 and OM System OM-1.
Sigma 19mm F2.8 DN is also available in Sony E mount.
Focal Range
Panasonic 25mm F1.4 II ASPH is a prime lens with fixed focal lenght of 25mm which has an effective (full-frame 35mm equivalent) focal range of 50mm when used on a FourThirds format camera. Sigma 19mm F2.8 DN is a prime lens with fixed focal lenght of 19mm which has an effective (full-frame 35mm equivalent) focal range of 28.5mm when used on a APS-C / DX format camera.