I tried openwrt first, and indeed, the network configuration was much easier, but then everything else was much more difficult and time consuming. Even system updates seemed overly complicated. I plan on running a few things on it, like zoneminder and syncthing, that will be much easier to maintain on debian
As for the reason, I got no more free ports in my router, and If I added another regular router, I wouldn't be able to run software on it, and would need an additional device, so this one allows me to add just one more device to the network. Well, considering that I manage to properly configure it...