I would have opted for steel studs and drywall, much easier than dealing with lightweight concrete. You would have had to plaster or cover the lightweight concrete with studs and drywall anyway... right... 
Since you don't have a wall there today, it won't be a load-bearing wall, so you don't need to go all out with lightweight concrete unless you want to for fun/learning how to masonry/plaster.
Since you don't have a wall there today, it won't be a load-bearing wall, so you don't need to go all out with lightweight concrete unless you want to for fun/learning how to masonry/plaster.
It probably depends a bit on what is going to be next to the wall as well.
We are going to build a new wall that will be between a shower and a sauna in our basement and will be tiled on both sides. There, we have been recommended to use masonry. The other walls we will frame up.
We are going to build a new wall that will be between a shower and a sauna in our basement and will be tiled on both sides. There, we have been recommended to use masonry. The other walls we will frame up.