Has anyone uses both ?, ive used a DA before but not the strip disc.

if you're talking about the 3M type mesh discs, they both work just as well, but a box of 80 grit d/a/ is probably going to be cheaper than x# of stripping discs. The d/a/ contact area is also a slightly larger area than the mesh discs, so it goes a bit quicker. My .02

I've used both. The stripper discs are way faster, but they wear out quickly and cost a pretty penny. They'll also destroy rubber, filler, softer plastics etc. I use both, depending on how easy places are going.