The cracks don't need to be vertical (just straight) to obviate the need for long slings. Also, the whole route need not be straight. Use long draws where the route angles and short draws where it's straight. Saves time + energy to use draws or not have to extend your trippled slings on every piece of gear.
In the vantage accident, it seems likely that a biner got loaded over one of those incut edges very common at vantage. If memory serves, it was the gear side biner that broke, not the rope biner, so it didn't matter how long the draw was. I could be wrong about that.
Fact remains, most (yes most) of the time, clipping directly to the cam, a short draw, or trippled sling is fine.
RE: the original question. If you are primarily sport climbing, get a dozen draws and maybe four 24" (60cm) slings. If primarily trad/alpine climbing, get ~10 24" slings and couple of doubles and take a few quickdraws along. The mammut 8mm slings are obviously the best.