Size and Weight Comparison
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 30mm F2.8 DN weighs 135g, 34% (70g) lighter than the Panasonic 25mm F1.4 II ASPH's weight of 205g.
Both Panasonic 25mm F1.4 II ASPH and Sigma 30mm 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 Panasonic GH6, OM System OM-1 and Panasonic GH5 II.
Sigma 30mm F2.8 DN is also available in Sony E mount.
Panasonic 25mm F1.4 II ASPH is a prime lens with fixed focal lenght of 25mm which has a 35mm equivalent focal range of 50mm when used on a FourThirds format camera. Sigma 30mm F2.8 DN is a prime lens with fixed focal lenght of 30mm which has a 35mm equivalent focal range of 37.5mm when used on a APS-C / DX format camera.