A couple of big picture thoughts to begin with:
While crop products like almonds, oats, rice, peas, etc. don't completely eliminate animal welfare concerns (because an indirect outcome of crop production can be harm to surrounding wildlife), these plant-based milks allow consumers to avoid the notable inhumane practices towards animals on industrialized dairy farms. Not all dairy farms treat animals inhumanely, but the vast majority in the U.S. have questionable practices. For more about humane forms of dairy, see Cornucopia and Certified Humane.
Non-dairy milks can be purchased heavily sweetened or unsweetened (with options in-between). For most people in developed countries, consuming more added sugars isn't a smart idea for long-term health. Further, sugar production presents an environmental burden. So, when possible, aiming to get non-dairy milk lightly sweetened or unsweetened makes the most sense for personal and planetary health.
Whenever someone is thinking about adding a new food/beverage into their rotation, it's worth asking the question "What's the alternative?" In other words, if you eat or drink X, what are you not eating or drinking? When it comes to milk, this is especially worthwhile to ask, because a straight swap from cow's milk to a non-dairy option will offer pros and cons, but rarely is it an equivocal nutritional swap. While drinking any form of milk (dairy or non-dairy) isn't essential for human health, some people do rely on milk as a source of important nutrients in their diet, so it's important to know the nutritional trade offs.
There's an obvious benefit or detriment to any one of these milks when considering food intolerance/sensitivity. If someone is allergic to tree nuts, then almond milk is a bad idea. If someone doesn't tolerate quinoa milk, then quinoa milk is a bad idea. And so forth.
Pros: Offers beneficial fats. Not a very strong taste. Good for low-fodmap eaters.
Cons: Doesn't offer much overall nutrition, as most store versions of almond milk contain mostly water (this changes if you make it at home). Almond production, especially on farms without any sustainability measures in place, can have negative outcomes on the environment (this goes for all tree nut based milks).
Pros: Legumes in general offer a lot of nutritional bang for your buck. You get some beneficial fats, protein, fiber, vitamins, and minerals. Also, when grown under certain conditions, soy can be a more environmentally efficient form of milk than most others (including tree nut and cow's milk).
Cons: If someone consumes high quantities of soy foods each day, along with soy milk, this might be a cause for concern (I would echo this with any single food that dominates ones diet).
Pros: Generally a more environmentally efficient crop to grow. And oat consumption is linked to beneficial health outcomes.
Cons: Conventional varieties of oats are treated with a notable pesticide (glyphosate). Residues can be of concern when consumed regularly over time.
Pros: Good for low-fodmap eaters.
Cons: Arsenic was applied to crops in the 1970s to control pests, and it accumulated in the soil. Now it turns up often in rice. If someone is consuming whole rice, rice crackers, rice protein powder, and/or rice flour, then they should be concerned about getting too much arsenic in their body (for more, see here).
Pros: More environmentally efficient to produce than almond, walnut, macadamia, and cashew milk. If someone isn't getting any saturated fats from other sources, this will offer some.
Cons: Some would argue that too many of the saturated fats in coconut milk might present negative outcomes with cardiovascular health. It's likely less of an issue when someone's diet is made up of mostly unprocessed foods, and overall fat intake is balanced (equal amounts of unsaturated and saturated fats being consumed).
Pros: All tree nuts contain a mix of beneficial fats. But nothing notable beyond what you'd find in almond, walnut, or macadamia.
Cons: There have been reports of human labor concerns related to cashew production overseas. The chemicals applied to cashews can be very toxic, especially to the laborers handling them.
Pros: Can offer a creamy consistency/taste for baking. Good for low-fodmap eaters.
Cons: Like other tree nuts, there's a steep environmental cost in production.
Pros: Hemp is one of my favorite crops, as it offers a lot of nutrition with not a lot of negative environmental repercussions. Good for low-fodmap eaters.
Cons: Tough to get from the U.S. due to legal barriers around hemp farming.
Pros: Nothing stands out. To get the most nutrition from quinoa, you're probably better off eating it whole.
Cons: American demand for whole quinoa has already led to some economic repercussions in areas of the world that produce quinoa as a staple. Putting quinoa in milk form might skew these economic repercussions even more.
Pros: Similar to soy, this offers a nice mix of nutrients, including fats and proteins. An environmentally efficient crop to produce, especially when grown on a sustainable farm. Good for low-fodmap eaters.
Cons: Peanuts can contain molds, mostly depending on how they're grown/stored.
Pros: Americans consume a staggeringly low amount of legumes (7 pounds per person per year), so I'm in favor of any method to boost intake, including pea milk. Consumption of legumes is linked to all sorts of beneficial health outcomes. Also, legumes tend to be an environmentally efficient crop to produce.
Cons: Nothing I can think of when consumed in reasonable amounts.
Pros: Most obviously, it's a nice product for someone looking to get more protein in their diet.
Cons: A bit more processed, which could have questionable long term health outcomes.
Pros: In the world of tree nuts, this one is less commonly consumed, so it offers a way to expand variety in ones diet.
Cons: Like most other tree nut milks, it doesn't offer much in the way of substantial nutrients (unless made at home). And it has the environmental cost that comes along with tree nuts.
Pros: A way to potentially use bananas that are about to go bad and be wasted.
Cons: Bananas are one of the most popular fruits in America, so I'm not sure incorporating them into milk does us any favors in terms of expanding our dietary diversity. Plus, in milk form, it doesn't offer much in the way of nutrition.
Pros: Walnuts are one of the notable plant sources of omega-3 fats. A fat that most people aren't getting enough of.
Cons: The environmental cost that comes with tree nut milks.
Pros: Seeds are generally nutrient dense and environmentally efficient to produce.
Cons: If someone is also eating flax, adding flax milk as well might be a bit much for the body on a daily basis, since flax is a rich source of lignans.