Not a pilot at either airline but used to live north of Seattle (Whidbey Island) so I know the area well. Otherwise, my situation was recently very similar to yours.

My two cents.. Go for Horizon. As much as people ***** on here about Horizon, if you're local and care more about staying local and commuting less, it seems like the best bet.

If you're guaranteed the 175 as you say, then you'll get SEA right out of training and perhaps PAE later on since QX will be flying the 175 out of there too. Given that Compass isn't a local company and may or may not exist in 5 years let alone be in Seattle, it seems like a no brainer to me that you'd go to QX (even on the Q400) if quality of life is more important to you than upgrade time. If upgrade is more important, maybe go to Compass instead, but do so with the risk of having to commute if Compass leaves, and knowing that the majors are hiring FO's with no TPIC right now so how important is upgrade, really?