Choose Alt-Wiedikon if it's noticeably quieter (52 vs 58 dB), it scores higher on safety (7.5 vs 6.5/10), it has better green-space access (6 vs 3.5/10).
Choose Werd if it's CHF 100 cheaper per month, the commute to HB is 4 min shorter — more central and connected, there's a denser restaurant scene.