These cameras are loved by street photographers, casual landscape photographers, documentary / environmental portrait photographers, and there's a significant Japanese lifestyle photography scene ... I often wonder if Sigma has this market in mind, which is not so visible if you're not in Japan or don't know where to look on Instagram (dig into the #sigmafp / #sigmafpl tag and look for washed out / blue-tinted photos of flowers/nature, for instance).
The major downside is no stabilization, which will severely limit the shooting envelope compared to these other cameras. I shot with a Sigma FP for awhile and the combination of poor autofocus, no stabilization, no viewfinder, and it still being heavy compared to, say, a Fujifilm camera, made for a very limiting experience. This will, however, be a user-experience upgrade for people who are happy with FP (which, honestly, I still miss sometimes).
"Worse glass" is a religious position if we're talking about Sigma glass. Especially considering how likely it is that any given name-brand lens is actually a Sigma design, or a Sigma design and build.
GR III = ultra-compact, fixed focal length, $1000, poor autofocus
Sigma BF = compact, interchangeable lens, $2000 + lenses, ??? autofocus
Leica Q3 = compact, fixed focal length, $6000, reliable autofocus
These cameras are loved by street photographers, casual landscape photographers, documentary / environmental portrait photographers, and there's a significant Japanese lifestyle photography scene ... I often wonder if Sigma has this market in mind, which is not so visible if you're not in Japan or don't know where to look on Instagram (dig into the #sigmafp / #sigmafpl tag and look for washed out / blue-tinted photos of flowers/nature, for instance).
The major downside is no stabilization, which will severely limit the shooting envelope compared to these other cameras. I shot with a Sigma FP for awhile and the combination of poor autofocus, no stabilization, no viewfinder, and it still being heavy compared to, say, a Fujifilm camera, made for a very limiting experience. This will, however, be a user-experience upgrade for people who are happy with FP (which, honestly, I still miss sometimes).