I have used an Airport Time Capsule and a USB hard drive attached to an Airport base station and both were painfully slow, so I suspect that speed is more a function of the backup device than the connection. With a "mature" Time Machine backup set — one that has been in use for a long time and has potentially hundreds of thousands if not millions of multilink connections — Time Machine backups, especially the daily, weekly, and monthly consolidations eat a LOT of CPU cycles connecting all the dots (links) and the CPU can easily become the time consuming factor. The only cures for that are:
  1. A faster CPU
  2. Erasing the old backup set and starting over from scratch
I have no direct experience with them, but I have heard good things about the G-Tech offered by the Apple store (at least in the U.S.).
SIDEBAR: There are some intriguing features of Apple's APFS system that hopefully could evolve into a better, faster, even more flexible Time Machine, but that is a major project in itself and will take time to develop and implement. Maybe in MacOS 10.14 but I would love to see it sooner.

Last edited by joemikeb; 11/04/17 01:50 PM.