My guess is since the pick angle is reversed on the way down (I’m talking about the angle where the point of contact is the vertex, the string is one side, and edge of the pick is the other), the feel is much different. Now technically it’s the same angle just flipped 180 degrees, but it will feel different against your fingers and thumb, since the other side of the pick is making contact. Another likely case is that if you play down strokes more often, the pick is more worn down on that side too.
The other angle that changes is the angle made between the plane/face of the guitar and the face/plane of the pick. If your hand remains in the same position, this angle will not be reversed, but will be x moving one direction, and 180 - x in the other,
If you can get your descending right hand to look like the mirror image of when it’s ascending, I think it will feel better. You can do this by tilting your picking hand to get that first angle, reversed.
Another option, which will only work with strict economy picking, is to have no angle between the pick and the string, and perpendicular to the face/plane of the guitar. This will not allow you to have and escape stroke, but as long as your strictly economy picking, you wont need one. Loosen up your grip on the pick, and allow the strings to push the pick one way when you’re ascending, and the other, descending.
Unless you are very partial to the sound of either ascending or descending, I recommend practicing them equally. This will help level out your abilities going up or down. Practicing one direction more would be like going to the gym and doing bicep curls with different weights in each hand. The one you practice more will inevitably be stronger.
Hope this helps!