Distilled water is probably all in all a better option than photo flo, assuming you have a ready source of distilled water nearby (i.e. a close grocery store that sells it, or a car).
No, Photo flo with distilled water is better.
Photo flo is usually the most toxic chemical in the dark room, for one thing.
Photo flo 600 is toxic if the concentrate is drunk but it is a thick liquid and I imagine is quite hard to accidentally get down and keep down. More dangerous things around the house include laundry bleach, dish washer tablets, oven cleaner, car radiator fluid, and petrol. As far as I can discover there has never been a single recorded instance injury to anyone anywhere through the use of Photo flo 200 or Photo flo 600.
It also requires yet another special container and you often want to save it for a few uses so you don't use up unnecessary amounts of photo flo
Photo flo comes in its own bottle. I use 5 drops of Photo flo per film so 1 litre of Photo flo 600 lasts me 4000 films on a discard after one use basis.
And it can be a little streaky if you use too much, blah blah.
True, but 5 drops in a litre of water includes a huge safety margin against overuse.
Distilled water on the other hand is obviously totally safe, cheap, can be used in any container or even just poured over, and just like photo flo, does not require any squeegeeing or anything else (there is nothing dissolved in it to create spots with drying, so it doesn't matter if it dries in individual droplets or not, unlike tap water).
An individual drop of distilled water will leave a drying mark on film because of the differential shrinkage of wet and dry gelatin emulsion. If you enlarge the negative with a diffused light enlarger the mark may be too slight to see. With a condenser enlarger the mark will be obvious if it's in an area of smooth tone like a sky. If you are taking digital pictures of negatives then Photoshop fixes everything anyway so why care.
Here's a tip: after the final rinse in Photo flo hang the film at a 45 degree angle. The solution only has to drain across the film not down the entire length. And if there are any drops they gather at the low edge well off the picture area. Maybe I've been lucky with Photo flo but after about 30 thousand films so far so good!