Potassium content of winter squash

[Allen Wein]

I have on file the following note about the potassium content
of winter squash:

Potassium content: Butternut squash (1 cup baked) 1200 mg
Acorn squash (1/2 baked) 750 mg (my notes don't say 1/2 *cup*)

This was recorded from "Laurel's Kitchen" by Laurel Robertson,
et al, 1977 edition.

The book "Food Values of Portions Commonly Used", 17th
edition, 1998 lists the following for potassium content:

Butternut squash (baked, 1/2 cup cubes) 290 mg (To compare
with above, this is 580mg per 1 cup) Acorn squash (baked, 1/2
cup cubes) 446 mg

The USDA National Nutrient Database, Release 19, lumps
together all winter squash.

"Nutritive Value of Foods: USDA Home and Garden Bulletin 72
(2002)" lists:

Butternut squash (frozen, cooked, mashed, 1 cup) 319 mg

So, if I'm at the food market, and butternut and acorn squash
are both available at the same price, which should I purchase
if my goal is to try to achieve a 4500 mg per day recommended
potassium intake?

Turning to spinach, "Food Values of Portions Commonly Used"
also lists the following for potassium content:

Spinach (boiled, 1/2 cup) 419 mg Spinach (raw, 1/2 cup,
chopped) 156 mg

Does the potassium content of a constant mass (say 100 g) of
spinach depend on whether it is raw or boiled? If so, why
would raw spinach have less potassium than boiled spinach?