Groups are a collection of objects, while a symbol is a special object in Vectorworks…
Vectorworks Tip 411 – Why Use Symbols Instead of Groups?
Symbols give you incredible abilities to attach information edit the information and control repeatable objects. In this example I’ve created a file with 100 tables. In the first file the tables are using the table and chair object. This file size is 10 MB. In the second example I’ve created one table and chair (exactly the same table and chair as the other file) made it into a symbol and repeated the symbol instance 100 times. This file size is .3 MB. This is a dramatic reduction in the size the file by using symbols. So my first reason for using symbols is that they’re much more memory efficient. I will be looking at using symbols to create and manage your libraries at the design summit in Chicago