With the 50-100mph time the spool doesn't really matter because everyone does them rolling and already at full spool at 50mph. I think the lighter weight will really help the RS put down a fast time.
I do like the longer WRX gears with this powerband, and I only imagine it getting better with more power. I'm still on the fence between a 6 speed or a built 5 speed. I think I'd prefer the built 5, but the 6 speed seems like the cheaper option and very reliable.