Rockguitarstar, I agree with Blue, go for 4-conductor cable and keep your options open for the future. There's no benefit from 2-conductor cable unless you have a vintage guitar and want to keep it period-correct.
Broken cord, again I'd suggest getting both pickups with 4-conductor wiring. The most versatile switching option would be to get two 3-way on/on/on mini-switches, which would let you have series/split/parallel wiring for each pickup. However, you'd have to drill 2 holes in the guitar ( :( ) and there's really not a huge difference in sound between split and parallel - most people prefer one or the other. I like parallel, because it sounds better (to my ears) than a split HB, plus it's hum-cancelling because you're still using both coils of the pickup.
Personally, I'd go for 2-way on/on DPDT switches rather than the 3-way ones. You can get them as mini-switches or attached to push-pull pots (which would save drilling holes in your SG!! :D ). You could use a single DPDT switch to split both pickups at the same time, but if you wanted series/parallel switching you'd need a separate switch for each pickup.
Sorry, I'm going on too long. The possibilities are endless. If you can, I'd recommend experimenting to see which wiring options you actually like and find useful - a Strat is perfect, if you have one, because you can get a cheap scratchplate and fill it full of holes without doing any permanent damage.