Not to be trendy, but I would also vote for qBittorrent. Used to use uTorrent but the multi-platform availability of qBittorrent and its very stable performance won me over now a few years ago.

Go open-source.

+1 for qBittorrent, happy to see so many other users here as well

Deluge is also great for a headless client-server setup

Been using uTorrent for years, but qBittorrent seems to worth a try as many people mention it.

I use utorrent for Windows and qbittorrent for Linux (Ubuntu).

rtorrent-rutorrent in seedbox and transmission in Mac, qbitorrent in windows

Only on seedboxes.
Transmission is good but slow to start.
rTorrent for tracker with quick pre.

deluge is great for <5k torrents. you need more torrents? move them to rtorrent. this works fine

rtorrent/rutorrent

has anyone tried ctorrent? its supposed to be even smaller than rtorrent.

i use qBitTorrent