Transport is only half the comparison
Official visitor guidance lists both as usable on public transport, but WOWPASS adds shopping payments, app balance management and kiosk-based functions. That convenience is different from saving money on Seoul fares; neither product is the short-term unlimited Climate Card.
Loading and leftovers
T-money is widely sold at convenience stores and station information centres. Visitor guidance warns that ordinary T-money purchase and top-up may require cash, so the cash planner treats transit loading separately from normal card spending. WOWPASS has its own kiosk and app workflow and can return its payment balance through kiosks.
A low-maintenance decision rule
If you want the fewest concepts and already have a reliable foreign payment card, start with T-money. If you value an app-managed visitor payment product and its kiosk network, compare WOWPASS. Then separately check whether a Climate Card would reduce the Seoul transit portion.