the Urals were biult more as tropp transporters and mobile command posts etc, they ride higher and have thinner tyres and a different front grille than the Kraz.
ural
the Kraz are heavier vehicles built for goods transport & as FATs, they ride on lower profile thicker tyres
kraz
To add to that, the UralAZ-4320 trucks are meant as troop carriers while the KrAZ-255B was meant to carry heavy loads into the marshes of Siberia for the development of the USSR. KrAZ-225B was developed specifically to replace Tatra-111. The thick tires are to work in molten permafrost which results in slush. UralAZ, KamAZ, ZiL on the other hand focused on troop transport. MAZ-535 was meant to be a tank transporter capable of terrain that KrAZ was meant to work in.
In India, we have had plenty of MAZ-535, KrAZ-255B, and ZiL-131, but I have never seen UralAZ or KamAZ trucks in India, save for the recent commercial ones. This is because, MAZ was in the Belarussian SSR, KrAZ in Ukrainian SSR, and ZiL in Moscow, RSFSR, and it was easy to export from these factories to India, while UralAZ (Chelyabinsk) and KamAZ (Tatarstan) were in the middle of RSFSR and difficult to export to India.
The task of KrAZ in India is to act as artillery tractors. Such tasks can be done by other trucks as well. Using KrAZ in India for artillery tractors seems to be an overkill.