Personally I prefer soy milk since it generally requires the least resources and also has the highest amount of bioavailable protein.

Oat is pretty good though.

I didn't like soy milk at all when I was younger (like a teenager). It had a weird aftertaste and texture. I don't know if it has changed since then or not, but now I also find it generally the tastiest.

I also use organic soy milk (since it is usually the only type that doesn't have gums or other ingredients....just soybeans and water) to make really simple plain yogurt too. I just break open a probiotic capsule or two into a 1qt tetrapak bottle, shake it up really good, divy up into 1c mason jars, and run the Instant Pot Yogurt setting for 15-16 hours.

That yogurt gets made into parfaits or overnight oats (with some date syrup if I can't find it...or just maple syrup to sweeten). Sometimes I'll even make a really good soft serve frozen yogurt (mix 1 part sugar to 4 parts yogurt, freeze 6+ hours, put it in a good blender, add fruit or vanilla or cocoa (or all!) as desired.