I had the pleasure of sitting here for the Mariners - Padres game last year when they were in town for an inter league series. The Padres were a team I had never seen before and rarely come to Seattle, so I thought...why not?
My view of the field was a good one, even from row 37 near the top. You may want to sit below row 25 just for safe measure because some fans may not share the same perspective that I share. But 143 is almost in the middle between the infield and outfield so I could see every inch of the field, no problem. But the first base line is definitely a more attractive area than the third baseline in my opinion because you're closer to the Mariners dugout and can see the scoreboard much better.