Original poster here. I ended up with the RAVPOWER one, and I'm very very happy with it. It's not too slippery and it's not too choosy about position, it just works every time. It's perfect. I have two, and I'm thinking about getting more. I'm really loving the wireless charging more than I thought it would. I had gotten so used to what a dang pain in the neck it is to put that usb plug in facing the right way that I didn't realize how great it would be to never do that anymore. It's such a pleasure to just put it down when I'm half asleep at night, and to just put it down and pick it up whenever during the day. It's always charged, how nice. Now if only there were charging stations everywhere out in public!