Considering the speed patten is flown at, the drag from anything on the plane ( baring airbrakes ) like cheek cowls fixed gear etc is really quite negligible. You really have to look at it as a whole system rather than saying wide bodies fly slow. The wider bodies tend to get pushed around more in a cross wind, so they need rudder correction to hold the heading, this crabbing slows the plane down. Wider bodied planes can be built lighter, the strength comes from the shape and size not the amount of material there is holding it together, which gives a lighter wing loading. The wide bodies are usually powered by well behaved 140 YS, OS or webra, they have loads of torque which means they can swing a bigger prop, which means that you can have a lower pitch to get the same thrust. This bigger prop gives a greater flywheel effect, combined with the new well behaved engines means a verrrrrrrrrry low idle, low enough that the prop is supposedly creating more drag than thrust, giving a slow downline speed. Then you have to think about the people that are flying the wide bodies, they probably have several years of pattern experience so they don't forget to shut down the throttle when coming over the top of a humpty bump that sort of thing. You put all of this together and you have a graceful slow package.

Matt