The Caribbean - Aruba or Grand Caymen

planning a 3-4 day trip in October (next few weeks). Any recommendations on which island is better? I would be staying at the Westin resort property on either island.

I assume both are fairly commercial and expernsive and not sure either will have more local character and I assume the activities are similar on both.

thanks

Both AUA and GCM remind me of southern Florida, although AUA just might be slightly more exotic. Both have nice beaches, excellent diving and great restaurants. AUA has casinos, and is much more liberal. GCM is buttoned down. If it's for a very short getaway, flight times and schedules might tip the scales one way or the other.
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13F

recently upgraded Westin in AUA located on a great beach

You might want to check out this thread (http://www.flyertalk.com/forum/caribbean/754809-honeymoon-aruba-grand-cayman-june-08-a.html). It asks (and answers, extensively) the same question. It's for a different month (June) and a different purpose (honeymoon), but most of the replies aren't specific to either of those points, other than discussing when hurricanes are likely.