When I moved to AUH first I lived in both of them for 3 months each.....!
Yas Island is a little remote. Taxiing into the Corniche is probably 60 - 70 AED these days. But it is nice and relaxed. Pool is great. Yas Links is next door if you play.
The IC is far more convenient for the city, being almost on the Corniche. Its old school by Abu Dhabi standards, but still a classy hotel. Rooms are ok, but frayed around the edges. The pool options have increased recently as they put another one in down near the shoreline (you have a beach of sorts also).
Both have some good restaurants. The breakfasts in both are excellent, with the IC shading it purely on the vast selection.