Well, if its between Nickel Lo-Riders and "Hi-Beams" I would say its Nickel Lo-Riders.. I don't hear Stainless Steel on a Jazz Bass there... Then again depending on the point of the tune it could be SS...
I would guess either a Nickel Lo-Rider or SS Lo-Rider
According to this interview with Bass Guitar Magazine Paul uses DR Hi-Beams which he barely changes. Interesting.. I always thought he used Lo-Riders although I guess they are both stainless roundwounds.