Not so sure about slower lenses and fewer options for available light shooting. I used a roll of Ilford Pan F in my ETR hand-held a few weeks ago, wasn't hard to keep the shutter speed up around 1/60-1/125 and the aperture around f5.6-f11.

As for lenses my 50mm and 75mm are both f2.8, that's only a stop slower than the 50mm f1.4 most 35mm systems have as a premium lens. I can shoot with those two and my 150mm and 200mm lenses hand-held even on overcast days with a roll of HP5 in the back. Shutter speed around 1/250 and apertures around f8-f5.6.

What 35mm does better is telephoto, and this is where available light does come in. I have a 200mm lens for my ETR system but even with the 2x teleconverter it's still only equivalent to something around a 240mm lens on 35mm, and you need strong sunlight even with Ilford HP5 as your maximum aperture works out at f9 or so with the TC taking two stops away. I usually try to shoot a stop or two down from wide open as most lenses perform better there, so now you're looking for conditions to support 1/500 at f16. This doesn't generally happen for most of the year here!