I've got the Modulo spoiler on my FD at the moment but previously had the Mugen. IMO the Mugen has the best lines/shape which flows with the Civic, but if you're going for a more subtle look, the Modulo does well.

Not a fan of the ducktail ones especially some of the eBay ones- there are other guys on here who have bought and seen the plastics warp over time in the heat creating a weird 'ripple effect'.