'59 Bridge has more low end, less treble, and more output than the Jazz Bridge.
This is despite the fact that the Jazz Bridge is spec'd with the same magnet and more wire (both of which are presumably 42 gauge).
That means the difference must be in how the coils are wound, or in how the magnets are charged.
They have never advertised that the magnets on either of these are softened in strength.
I believe '59s are wound on the old Gibson machine, with whatever winding pattern it uses.
The Jazzes must be wound with a different winding pattern, resulting in different coil dimensions, I'd think. Maybe they are a bit more neatly wound, which would theoretically result in smaller coils even with a bit more wire length.
The pickups are in the same basic family (A5, 42 AWG, PAF-based pickups), but the '59 gives a "meatier" tone.