If you are gonna be adjusting it often, I'd go with the DD style. It's lighter and cheaper. However you do need to buy the more expensive cover.
The sling shot really feels more like a set it and forget it kind of deal. I love mine, but if you are wanting to do several changes for drag racing they can be a chore. The cover has to come off every time, then the sling shot cover has to come off as well. For a trail or duner set up they are a pretty slick deal though. You don't need a pricy cover, and they take minimal work on the stock cover to work.