Ektar is not an inferior film as Portra, but another professional film. It has smaller grain and a saturated color usually more suited for landscape and general photography, other than portrait and fashion, that is what the palette of Portra was created for.
So said, I expected different pictures of such combination of film and lens. Ektar gives saturated, vibrant colors and a huge exposure latitude and the Minitar lens is famous for its contrast (well, and for the vignetting, of course). Maybe you pushed it?
Andrés PB