It was a intial phase of transition where dishtv needed time to settle d2h into dishtv ecosystem and for that dishtv pushed d2h only for South where dishtv wasn't strong as for time being in intial phase because south was d2h brand's strength and durin this period dishtv completed migration of dishtv south subscribers to ST2. Durin this period dishtv offered 3 options to broadcasters i.e 1) for South Target market ST2 ( d2h ,dishtv(migrated ) 2) for North East & south target market ses8 ( Dishtv ) and 3) both the satellites SES8 & ST2 for Pan India market. Some channels has kept exclusive for each satellite.
Now, after couple of years Dishtv has launched d2h into North East market.
Now, which ever south channel is launched on ST2 is available for both brands dish & d2h,same with north SES8 where migration of d2h set top box has enabled alongside dish.
Both brands are operated by Dishtv with same backend team, from same infrastructure,with same configuration,set top boxes are manufactured for same dish infra.d2h subscribers are subscribin Dishtv DTH service under d2h brand name.
Now about difference, dishtv has two teams in which one team pushes Dish brand into market with various offerin and another team pushes d2h brand into market.