The Portland Timbers are a decent MLS side, with decent playoff history. They make the playoffs fairly often, even won a title. What they are not, is a good MLS Playoffs side, or a good USL Playoffs side. Their latest coach may be a good playoffs coach, but has never been tested over more than two games in a single year (Sunday will be his second playoff game of 2018).
Sure, they beat the Sounders in the only MLS Cup Playoffs meeting. They have not beaten Brian Schmetzer in a playoff series (Schmetzer is 3-1-0, +3 in their USL playoff meetings).
Portland made the playoffs three times prior to this season (this is their eighth season). With their win over FC Dallas they are now 6-3-4, +3 in their MLS Cup Playoff history. In 2015 they won the MLS Cup; this was before Seattle won an MLS Cup. It was first, which is what you mention when you only have one trophy.
Brian Schmetzer has more playoff wins than the Timbers do in their MLS history.
The Portland Timbers were only active in the USL and A-League from 2001 to 2010. In the 90s they were not a professional soccer team. In their short time in the lower divisions they advanced to the playoffs seven times, which is better than every other year (their current joke about themselves). During that stretch, they never won the USL Championship and didn’t take the Commissioner’s Cup until the Sounders were busy winning trophies in MLS. In the lower division playoffs they went 5-10-3, -9 (in no year did they have a positive goal differential).
Schmetzer, again, had more wins than the Timbers at that level, despite participating in fewer seasons.
Giovanni Savarese as Cosmos Coach
The NASL playoffs were tiny, like the league. Just two, and later four, teams participated in one-leg knockout format. Gio won three Soccer Bowls when he coached from 2013 to the 2017 season. His record was 4-2-2, +1. That’s ok, I guess.
Brian has coached for 10 years, only missed the playoffs once, made the finals half the time, won it three times, He has a record of 17-8-8, +10, which is kind of like 4-2-2, +1, but better.
The Timbers have history. It’s just not good, unlike Seattle’s playoff history, particularly under Brian Schmetzer.