Simple ergonomy, advanced functions such as :
1- astrotracer : only on Pentax,
2- pixel-shift : only on Pentax (but other use resolution enhancement via multi-exposure like Olympus and Fuji)
3- composition adjustment : only on Pentax
4- TAV mode : only on Pentax (equiv. to M mode + ISO auto on GR III and other brands)
5- green button : only on Pentax
6- sensor shake reduction : first on Pentax (and Minolta)
7- effective "all weather"/"weather resistant" sealing : systematic on Pentax after K-S1
8- pentaprism versus pentamirroir : systematic on Pentax since K-S1
9- in-body raw development : first on Pentax
10- DNG raw format : first on Pentax (and Leica)
The actual technical "limitative" exceptions being :
- 1/125s to 1/200s maximum flash synch on flagships (but largely improvable with HSS external devices >1/8000s or LS "old" lenses >1/500s)
- maximum 33 AF points in SLR mode on flagships (until next K-2)
- no 4K video, and low profile video tech in general