A housing can either take a bulb or a retrofit LED ring that sits on the end. If you use a bulb (LED or otherwise) then the angled housing can be of benefit, by keeping the beam pointed in the downward direction. However if you're using a flat LED ring, there's no benefit to using an angled housing, because it's going to sit on the slope anyhow.
If you're concerned about lighting the area in a downward fashion, you can either use an angled housing:
with a LED bulb in it:
or use a standard housing:
with what's called a "gimbal" fixture. A gimbal fixture looks like this:
And will allow you to compensate for the slope in the ceiling, by pivoting the fixture inside the housing.