The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Leica Summarit-M 90mm f2.5 and the Leica APO 75mm f2 ASPH for their suitability to various photography scenarios:
Size and Weight Comparison
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Leica Summarit-M 90mm f2.5 weighs 360g, which means it is 70g (16%) lighter than the Leica APO 75mm f2 ASPH which has a weight of 430g.
Filter Threads
The Leica Summarit-M 90mm f2.5 has a filter size of 46mm whereas the Leica APO 75mm f2 ASPH has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 46mm filters that we recommend you to consider for the Leica Summarit-M 90mm f2.5:
And these are the 49mm filters that we recommend for the Leica APO 75mm f2 ASPH:
Lens Mounts
Both the Leica Summarit-M 90mm f2.5 and the Leica APO 75mm f2 ASPH has the same Leica M lens mount. Some of the latest released cameras that are compatible with the Leica M lenses are Leica M11 Monochrome, Leica M11 and Leica M10.
Focal Range
Leica Summarit-M 90mm f2.5 is a prime lens with fixed focal lenght of 90mm.
On the other hand, the Leica APO 75mm f2 ASPH is a prime lens with fixed focal lenght of 75mm.