It used to be like that but they have been improving. Unless you are into gaming or custom roms i think mdtk are a good choice too.Especially for midrange priced devices.While you could say that for most SoCs (SD, Kirin, Exynos) mediateks have always had the bad reputation of being closed source and not being upgraded to the latest android version. And the gpu it is paired with has both poor performance and closed source.
But i understand some people won't trust them considering their past.
I would personally go for mdtk over SD615 for example