Same here: my selection boiled down to Borg vs. Restic. I started with Restic because my friends used it and, while it was perfectly satisfactory functionally, found it unbearably slow with large backups. Changed to Borg and I've been happy everafter !
What is a "large" backup? Slow to backup locally or slow to backup over a network? (obviously you are not saying its slow without understanding the network is inherently slow, but more along the lines of maybe its network protocol is slow.)
Those were only about 10 TB - home scale, and over SSH across 2 to 10 ms. I was coming from rdiff-backup, which satisfyingly saturated disk writes, whereas I didn't even understand what bottleneck restic was hitting.