That said, your answer raises a good question that I don't have the answer to--whether the owners of coops in Washington have to pay some type of personal property tax. With the exception of businesses, assessors tend to ignore personal property in Washington. If there is no personal property tax then there likely would be some tax savings, in part because the total current value of a coop is likely less than the total value of a condo, and in part because the assessor would not have good access to current sales data.
Similarly, I'm pretty sure the real estate excise tax doesn't apply when you sell, but there might be some other tax applied.
In a condominium you own everything from the surface of the walls of your apartment with title to a piece of real estate.
Lending is more specific in co-ops and you have to connect with a very specific loan officer who processes that type of loan. Most of the loans are underwritten by the National Co-op Bank. They typically require a 10% down payment.
Condominium lending is also more challenging than single family lending in that the underwriter typically wants to understand the health of the Condominium Association before they will commit to lending on the real estate. The health of the Association will determine whether the down payment requirement is 3%, 20% or 25%.
There is a requirement that the co-op board approve (without any discrimination against protected classes) any new buyers and that is done with an interview process. I see it as a benefit because it also an opportunity for the buyer to meet the board and if there are people you don't like you, as buyer, can move on. I wish Condominium Associations had such a requirement because it would save a lot of head/heart ache in the future.
If you'd like more information, email me me and I have a flier that goes into more detail.
Ownership in a coop is not a specific ownership interest in real property, but instead an ownership interest in an entity which owns real property. That ownership interest gives you a right to use a specific unit and the common areas of the building. With a condo you do own a specific interest in property which is considered real property and there is generally a HOA which governs the complex and maintains the common areas.
Beyond the legal differences, the main practical difference is financing of a coop is likely to be more limited. Due to the likely older age of the building and limited financing options, coops are typically less expensive, all other things being equal.
Call me if you need help.
Coldwell Banker Bain
Here in Seattle, co-op buildings TEND to have more deferred maintenance than condos. And many co-ops are pet-free, most are dog-free. Few have indoor parking.
BUT, co-ops also tend to be cheaper than condos!