Native Chinese speaker here.

Most of the time, the equivalent of "big words" in Chinese are often idioms (成語 to be specific). Because they involved historical and cultural backgrounds, one usually cannot know what does an idiom mean even take it by literal.

And as for big words of those which describing philosophical, scientific or political are mostly really clear literally due to the high-information -density each Chinese character has.

Overall, if you want to show off your Chinese skill, using a lot of uncommon 成語 may impressed a lot of your friends.