we get very long stretches of rain
This does not make goats happy, they might melt

There are problems that go along with that, since goats are more of an arid-country critter. We get lots of rain too and the two problems that pop up over and over are one, they have a high mineral requirement and constant rains can leach that from the soil. And two, they can be very susceptible to foot-rot and other fungal stuff. I guess what I'm trying to say is that getting goats from a successful breeder nearby in the same rain might be more important than actual breed because they will be selecting for goats that thrive in your climate.
As far as mixed or purebred, mine are mixed because I'm cheap, but I have good does and I make sure to pick good quality bucks at breeding time because milking ability is important to me. In general, though, I think purebred breeders might be a little more careful than mutt breeders about the quality they breed.
Kinders are, I think, a nice compromise between milk and meat
if you get a good quality one. The problem being that almost no one considers milking ability when breeding Pygmies. Just breeding them to a
dairy breed does not guarantee that the offspring will have decent udders or production. However, that's all they were to begin with, a Nubian x Pygmy. If you want one and can't find one, get a Nubian doe or two and a Pygmy buck and make your own. If you get less than ideal udders, it gives you a goal to breed for.