The quality of life is great in Aventura and Sunny Isles Beach both.
One is called, like Beth said, a City of Excellence, and the other a Floridian Reviera.
The schools are very good in both.
Taxes are similar, and based on the assessment of the property. Assessments are based on the sold normal sales and short sales (not foreclosures) in these two cities.
If you buy a principal residence, your taxes will probably be about 2% of the purchase price.
Hope this helps,
Irina Karan, CDPE
Beachfront Realty, Inc.