I’m not trying to start a war here, just wondering what your takes are. They pretty much have the same concept of lightweight desktop, but with different toolkits.
I’m a KDE person myself, but I’ve had experience with XFCE.
I’ve tried LXQt in the past but never really gotten into it, perhaps the timing was just not right.
I liked Xfce a lot, and used it for more than a few years, until it migrated to Gtk 3. (Modern Gtk breaks things that I use, and forces UI decisions that constantly get in my way. It’s just not for me.) It has also become more memory-hungry over the years, so is no longer quite the lightweight desktop that it once was, although that’s not why I switched.
LXQt was first on my list when looking for a replacement, but I used it only briefly, because there were too many rough edges and little integration problems. It didn’t feel like a cohesive desktop compared to (old) Xfce. I imagine some of that was a side effect of ongoing work to transition away from Gtk. It was a couple years ago, so it might be better now. I still love the idea of it.