They're basically identical functionally, just the USG is Unifi enabled. It would be a side-grade step if anything.
Unfortunately, the only way around this to run a cable. These access points are very good, they just don't work miracles. Home hub 6 is probably just as sensitive as an AP-AC-LR and I don't have my AP-AC-HDs yet (middle of May delivery) but they should be a little bit better again. I started out by running two cables outside the house. You drill a hole in the wall where your internet comes into the building big enough to take 2 cables and then you drill a second hole roughly where you want to take the Internet. They you run the cable round the outside of the building and at each point fit a double RJ45 socket. CCS make a tool-less keystone module with faceplates so you don't need a punchdown tool. Two pattress boxes, 200m cable and two loaded keystone faceplates should be under £100. Any semi-competent handyman or aerial installer will be able to do it. Or, if you want to really spend money, you can use the AP-AC-Pro or -LR in a mesh configuration (they call it uplinking) where the first one is wired then the others are meshed into it, but they still have to be powered so you still need a PoE injector for each unit. The best option is to just bite the bullet and run a cable.