[jfengel]

The glycemic index of most milk substitutes (oat,soy,almond) are equivalent or greater than a can of coke.

That's true of oat and rice milk, but not of almond or soy. That's to be expected: the former two are made out of starchy grains, the latter two out of fatty nuts/pulses. Those are on a par with milk for glycemic index (~25).

The worst case ("obese cows on a grain fed diet in a feedlot") is also the common case: if you go to the grocery store and buy generic "milk", that's what you're going to get. Organic may be slightly better, though it's unclear. You can go out of your way to get more sustainably-produced milk, but you're going to pay at least twice as much for it.

That's a decent choice, though I'd be happier if it were easier to verify. (I don't trust the labeling of "grass fed milk", and locally-sourced milk that I can check myself is hard to come by.) The small comfort is that dairy cattle have to be treated relatively well, since they can't produce good milk if they're sick or abused.

[RamshackleJ]

Commercial beef feedlots vs commercial dairy feedlots are a mile apart, but unfortunately most dairy cows end up at the former after they hit declining milk production.

I'd recommend checking if you can go tour a local dairy, I've found that any quality dairy will let you do that and you can judge for yourself about the welfare of the animals. You're gonna to pay more but the nutritional value of a gallon of milk at $8 vs $2 is still well worth it imo.

I'd also really recommend looking into the health impacts of vegetable oils. Most milk substitutes are, at their core, emulsified vegetable oils. I found that the trade-offs were higher glycemic load(oat/rice), increased vegetable oils(soy/almond) or something that tastes nothing like milk (unsweetened coconut milk).