I'm also debating between Sheath and Paragon (leaning towards the Paragon.)
Funny enough, I had a Spigen Liquid Air for my old 13PM. It's way lighter than my temporary case but I don't really notice it weight-wise as much as I notice how less bulky it is while holding it. For the price you can't go wrong with it but when I first got it the back felt "dry" but eventually it became it became oily. (with heavy use) The drop protection was surprisingly decent, my old phone has no scratches just a little dust.
Do you think your old Sheath is bulky? More than anything, I'm hoping the Paragon feels less bulky.