I don't think the etymologies of the words support the go vs. be distinction. Neither word has a root -- like -cur or -cede -- that suggests "going." Literally, 'ubique' means "anywhere," while 'omnipresent' means "everywhere."

It is actually the suffix -ous in 'ubiquitous' that adds the notion of "seeming to be." Thus, something that is ubiquitous seems to be anywhere you look, while something that is omnipresent is everywhere, regardless of whether it seems that way to you.