The 28-70 is way too big and heavy. It weighs about 5 times as much as the RF35, which offers a faster aperture and IS!Yeah, but f/1.8 vs f/2.0... not a big deal. Especially considering the flexibility in focal length. Shall I choose a strict 35mm f/1.8 vs a 28-70 f/2.0? No brainer.
F2 is nice, but it’s still quite far away from f1.2 or f1.4.