It’s probably the pigmentation and/or texture; MAC e/s are hard to beat in terms of sheer selection, but many people find that the pigmentation is not up to snuff and thus more product has to be used, creating problems w/ the texture as well. You probably like the UD e/s because of their pigment saturation: less product is needed and the product can be applied more sheerly/lightly.
Alternatively, you can purchase low-end or drugstore brands as (here in the US, at least) many d/s brands are really catching up with their high-end counterparts in terms of quality (if not selection).