Choose Fluntern if it's noticeably quieter (42 vs 55 dB), it scores higher on safety (9.5 vs 7.5/10), it has better green-space access (9.5 vs 5/10).
Choose Hochschulen if it's CHF 150 cheaper per month, the commute to HB is 8 min shorter — more central and connected, there's a denser restaurant scene.