Differences:
1. The sides extended and are flush with the car, BRE has a large gap on the sides.
2. It stands up straighter. BRE is at a slight angle out.
3. It has a lip that hangs over the edge of the hatch. I assume this is removable if you dislike it.
4. It doesn't have a raised section on the right hand side like some do. Ie. The bit where toecutter put a fairlady emblem on.
The topstage spoiler fixes all of what I feel are design flaws in the BRE spoiler, I have test fitted one and it is excellent.