Either method can last for years if used carefully, but the community answers lean slightly toward removing the battery and card rather than relying on the camera’s USB port.

Why:

• Battery doors on Canon bodies are generally robust, and on some models are even designed to be removable for battery grips.
• SD slots are usually fine if handled carefully; with SD cards you avoid the bent-pin risk seen with CF slots.
• USB ports work, but repeated plugging/unplugging and opening the rubber port cover may create more wear, and a cable sticking out of the camera can increase the chance of damage if bumped.

One answer notes a practical counterpoint: if the USB port fails, you can still often use an external charger and card reader, while failure of the battery/card compartment could affect basic camera operation. Still, real-world experience in the answers suggests battery/card access is very durable when used normally.

Best practice: use whichever is more convenient, but if durability is your main concern, careful battery and card swapping is a reasonable choice. Avoid leaving compartment doors open, and don’t let a connected USB cable be stressed or knocked.