One of the the best things about these seats is that you will have a good view of the arch (which will be slightly towards your right as you look to center field from these seats).

Section 139, Row 16 Seat View
Section 139 (as seen from Row 16) has a fantastic view of the entire field

In addition, these seats are likely to be in the shade for the whole game so you can beat the heat.

You will not be on top of the field because there are lettered rows in front of numbered rows in this section (so row 21 is really like row 30). But this means you will have a fairly short walk to the concourse and will not have to fight the sun.