I used to see the tourist buses doing the day trip from Dubai to Abu Dhabi... People would get out of the coach on the AD corniche, take some photos, get back in, then presumably be driven back to Dubai.
The Sheikh Zayed mosque is spectacular, the dhow building yard is interesting, but after that, there isn't a lot to see in Abu Dhabi.
Yes, the buildings in Dubai are spectacular, but do you just want to drive around a motorway looking at buildings? 99% of both cities are less than 50 years old.
I'd give both a miss and head for Muscat where there's plenty to see if you get out of the city (town)

We even had Jimmy Carter (remember him?) here for the past couple of days...