Having used both, I prefer Scene Optimizer, but probably only because I'm more comfortable with it. LOD has a slightly better UI, and a bit more control with stuff like distances and such (stuff you'd usually see in more advanced software). I don't remember if you have to restart like you do with SO. But for Daz? Just grab whichever's cheapest and use that. They aren't that different. Either way, the same rules apply to both.
I do remember originally rolling my eyes at the whole "Better Scene Optimizer" bit. Let your software stand on its own, and if it can't, then go back to the drawing board. But that's nor here nor there.