Northwestern? Alexander’s? Coopers???

Anyone better then the other for LME??

They are all very similar, but slightly different in some ways, some of the liquid extracts are more fermentable than others, and others leave a sweeter taste behind. If for example you were making a big beer that you wanted to have some residual malty sweetness you would probably go with some John Bull as opposed to coopers, I don't use extract any more, and at one point had figured out which ones were most fermentable, but in short they are all so similar that it does not really matter. My one suggestion would be to exclusively use "Light" or "Extra Light" extract and get your color and unfermentable sugars from steeping grains.