My question is, if the critter power is the same than the adept power. A pixie has Astral Perception as an enhanced sense (which would be 0,25 power-points for an adept) and not 1 point like the adept power. Is this maybe a clue from the devs that this power should be cheaper?^^

Well yes, it should be cheaper, but the real reason it's there is because there wasn't a better way to do it without mandating the purchase of a quality.

I take this as a "yes-you can take astral perception as an alternative to the "astral perception"-power"^^

...which doesn't matter unless you are the GM, who is the one who typically makes a ruling on ambiguous rules interpretations.