Big,
If you are going sideways, its because your rear brakes have locked up. Most vehicles and drivers are not balanced well enough to similtaneously lock all 4. Lock the front and you can't steer. I belive drum brakes are more prone to locking since they are self-energizing. As the drum rotates, it tends to pull the shoe into the drum. Most stopping is done by the front brakes (due to weight transfer & load) and the biggest bang for the buck is by switching to front discs.
Repeated use, high loads and long descents will all cause a drum brake to fade. The drum expands as it gets hot and moves away from the shoes. Too hot and it would distort. The lining material for drum brakes just becomes less effective the hotter it gets, this limits how hot a drum can get and protects the brake at the expense of stopping ditance. When a rotor gets hot, it expands into the brake shoes and becomes more effective. Fade is much less an issue with a disc brake.
I can't see it on TV, but watching the Nascar/Busch guys at IRP, their brakes are glowing red goiong into the corners. A disc brake can easily be designed to work at 600-800F. Drums may be topping out around 400-500. Drums brakes pull due to differences in adjustment, brake shoe condition, drum condition. Discs don't pull because of their self adjusting characteristics. An oily or contaimined pad/rotor will still cause a problem. If you aren't mentally having to correct for pull you can focus on stopping. I also agree with Grigg that power discs are easier to modulate.
As others have said, tires are a huge part. Short & skinny are easy to lock up. Tall take more brake to stop. Wide should put more rubber to the road, but hydroplane easier. It's all a balance. Tread is important too. If you have average size tires
in good shape, changing them out won't solve your problems, I'd go front discs and work with the proportioning to get good solids stops and limited rear lock-up.
