This is a useful Belltown comparison because the structured records share the same neighborhood and high-rise type. Concord was built in 2000 with 206 residences across 13 stories. Ellington was built in 2001 with 204 residences across 12 stories. Both records are Belltown high-rises with a Walk Score of 97.
The published HOA ranges and amenity lists are where the structured comparison starts to separate. Concord is listed at $700 to $1600 with gym, concierge, and business center. Ellington is listed at $500 to $1000 with gym and rooftop. Those facts are useful starting points, not substitutes for current HOA document review.
I would compare the exact units side by side on monthly cost, floor, exposure, parking, reserves, rental policy, pet policy, and current building documents. The better choice is the unit and HOA position that underwrites cleanly for the buyer, not simply the building with the lower published HOA range or the different amenity list.