Choose Höngg if it's noticeably quieter (45 vs 68 dB), it scores higher on safety (8.5 vs 5/10), it has better green-space access (8 vs 2.5/10).
Choose Langstrasse if it's CHF 100 cheaper per month, the commute to HB is 10 min shorter — more central and connected, there's a denser restaurant scene.