I have a Domino but still use my Lamello biscuit a lot. I like that I don't have to think as much with a biscuit cutter as I do with the Domino. LOL. You can use each in different ways but the biscuit joiner registers off the bottom side while the Domino usually measures off the fence above the blade. This can make the Domino more fiddly. It is easy not to get it exactly square when balancing it on the end of a board. The biscuit joiner will just register off the workbench which more stable.
I agree with those above defending the strength of the biscuit. While the biscuit can slide end to end a little to make it easier to assemble, the sides are a tight fit. In addition to that they are compressed and will swell when wet with glue and get even tighter. I don't know where the idea came from that they are only for alignment but I suspect it got started when they first came out from traditionalists that thought only a hand cut mortise and tenon was acceptable.
I agree with those above defending the strength of the biscuit. While the biscuit can slide end to end a little to make it easier to assemble, the sides are a tight fit. In addition to that they are compressed and will swell when wet with glue and get even tighter. I don't know where the idea came from that they are only for alignment but I suspect it got started when they first came out from traditionalists that thought only a hand cut mortise and tenon was acceptable.