Do I need a cable-style lock or a rigid shackle?

Cable locks (like the Forge re-settable cable design) are easier to thread through awkward zipper pulls and around backpack straps, and r/HerOneBag commenters specifically ask for cable styles for train travel. Rigid-shackle locks like the Master Lock 4696T are sturdier and harder to snip, which is why mainstream press coverage tends to favor them for checked luggage. Many frequent travelers keep one of each.