I need to park at BWI for five days. It looks relatively cheap, compared to other airport locations, only $8-$10/day for on-airport parking. The off-airport places seems to be about the same prices, maybe a bit less with a coupon. So is it worth it to park on-airport? What are the shuttles like? From my experience at some other airports, the off-airport is not only cheaper, but you end up waiting less time for the shuttle. Is the BWI daily garage walkable to the terminals?

Thanks for any suggestions.