One big advantage of bivvy loos over traditional catholes is their utility in fragile or high-traffic areas where Leave No Trace practices discourage digging. They can be especially useful above treeline, on desert rock, or anywhere soil is shallow or impact must be minimized. Most modern systems do an impressive job of containing odor with double-lined bags and absorbent gels. Just be sure to practice sealing and packing out at home so it’s second nature in the field. A zippered “smell-proof” pouch for the used bags definitely helps keep your pack cleaner. Downsides are the extra weight (usually 400g+ with bags for a weekend) and the need to carry out waste, but many find the tradeoff worth it for convenience and minimal site impact.