ETB versus a booster box
What Trainer Case lists when you want sleeves and dice in the same wrap.
An Elite Trainer Box is a kit: packs, sleeves, dice, and a cardboard shell. A booster box is packs only. Trainer Case exists for people who want the kit, not a 36-pack case.
Price per pack is usually worse on an ETB. That is fine if you actually use the extras. It is not fine if you were promised a cheaper box and received a kit.
All listings here are unofficial. Marks belong to Nintendo, Game Freak, and The Pokémon Company.
FAQ
Do ETBs have the same pack art as boxes? Pack art can differ by print. Read the set code.