I've almost always used Dyneema wishbones, as I started with a Rob Allen railgun and thought they worked well. Light, simple, quiet, can be cheap, and less likely to damage your hands. Dyneema wishbones can last years but the outer sheath can sometimes become damaged.
However, I suspect that spearguns equipped by the manufacturer with articulated wishbones (like my Omer XXVs) are likely to be more accurate with the original articulated wishbones. They also last very well. I think accuracy is usually more important than mass (I have 2 superlight spearguns but mass wasn't the only or even main consideration when I switched them from metal articulated wishbones to Dyneema - but it was a consideration and nice to have

).
BTW I'm not a fan of screw-on bands, due to cost and limited availability (different manufacturers also use different threads). But there are articulated wishbones designed for use with bulk rubber loops - the ones I'm thinking of have a rod with a ball at each end; the ball goes inside the rubber, like a wishbone bead.
For 14mm bands, I think Dyneema might be the better option. Also, I would probably try using knots rather than beads. Metal beads are heavy and most beads are too big for 14mm rubbers - they often fit but bulge the rubber out too much I think. That said, some manufacturers equip their 2x14mm spearguns with hefty 7mm spears, so perhaps not that critical.