Its only around a 1.5hour drive from Dubai to Abu Dhabi, so I’d suggest it is a must visit if staying longer than 2 days in Dubai. The Sheikh Zayed Grand Mosque with its squinting bright white marble, beautiful interior and sheer scale is the obvious must visit spot, but also give yourself time for a drink in the luxurious pink Emirates Palace with its gorgeous terrace overlooking the sea.
Definitely worth the drive from Dubai.