Really depends on the display resolution. If you can see the pixels, it will detract from the overall experience. A slight defocusing could help blend the pixels together without causing distortion.
The Oculus part looks disappointingly cheap. Single lens, rather than compound (which is probably why it has that chromatic aberration). The support ribs on the bayonet flanges suggest it's made of thin plastic, probably flexes if you squeeze the sides of it. Hard to tell what's holding the lens in place, looks like it could pop out fairly easily if you tried. In comparison, the Microsoft part looks more like my vintage telescope eyepieces.