Well, one thing is that you can use the Flatline. Second, a CAR-15 stock.
But, it's also the feel of the gun. I love the feel of a 98 compared to any other gun I have owned/used/held. Mostly because I've gotten adjusted to it for the past 3+ years.
Plus, the Imp is almost as badly balanced as a BM2K. If you ever hold a Bushy, you'll realize just how much it wobbles in your hands, and I don't like that in a gun, personally.