The Specialized Crosstrail (front suspension) and Specialized Sirrus (hard fork) are both really nice bikes for that kind of riding.

They aren't SUPER light, but they aren't bad. They roll well and are easy to ride. I wouldn't want to carry one for 2 miles...but they aren't super heavy.

I'm assuming when you say "sandy beach paths" you mean a hard pack surface that has a thin layer of sand on it, not "ride on the beach itself". That will make a difference.

The best possible answer is to go to the Giant and Specialized dealers and test ride a bunch of bikes to see which one just 'feels right'. There is no 'best bike'. There is the 'best bike FOR YOU'. As long as it's a decent quality bike (both Giant and Specialized probably will be) get the one that feels easiest to ride. Your body shape and size makes a difference as to what bike frame geometry is right for you.