1.5hr will get you (probably, if on time arrival) just enough time to sample Al Sawfa, and considering that you actually want a quick city trip to Abu Dhabi, I'd say go with the 23hrs layover (with the widebody to CAI as a little bonus)

For 23hrs in Abu Dhabi, you can get a rental for dirt cheap (1 day rent is like 20$) and you can drive everywhere yourself. Must sees, as others have described, is the big Mosque, I'd also visit the F1 track area (if you're into motorsports) and/or the Yas Mall. One of the nicest malls imho. I'd skip on Ferrari world, though.

Abu Dhabi, the city itself, is much less "fancy" than Dubai, and you can actually walk around in most of the city areas.. plus, it's smaller and much easier to navigate. If you like it a bit quieter, there is a huge hotel area on Yas island near the airport, with a private beach access included (if you don't want to stay in Abu Dhabi city centre)

Other things I'd recommend: Take elevator up at Lulu mall (on the island vis-a-vis Corniche) - not even needed to eat at the café at the top, the ride is free and spectacular enough

Apart from that, most things will depend on the time of the year you'll be there.