x2.
I've seen folks with cheap jumper cables that couldn't get enough current to flow to get the car started, but it kicked right over with my 2 gauge cables. They might be bulky and expensive, but when you need them, good ones are worth it.

 

Usually just looking at the clamps will tell you if they are cheap or not, by a decent set and you will never have to by them again.

 

IMHO the deciding factor is weight. Big copper wire weighs more. If you want to "roll your own", check out a welding supply store, where they sell 1/0 welding cable (and smaller stuff also). Welding cable is very fine strands, so it is super wimpy noodle flexible, tough outer jacket. You can make an extra long set if you like.

 

I happened to be using mine last night and they are actually made from #1 welding cable, not #2.