Wonbderware (and all other HMIs) do a lot of the donkey work for you, and make animation easier.
In VB, you dimension a bunch of variables.
In WW, you create a bunch of tags.
Not too different.
In VB, you have to write code for each variable to get its value from the PLC at a specific address. WW is more like a spreadsheet (and can be editted in Excel).
When you go to animate an object, WW will give you a list of all your tags. In VB, you can get a list of your variables, but unless you were smart and gave all your process varaiables a common prefix, you won't know which are I/O variables, and which are not.
And sometimes you forget if this tag goes to the datapoint you think it goes to ("Is PRESSURE_OK the high pressure switch tag, or the permissive that says that I'm at atmospheric and it's OK to open the valve?"). A WW tag has a description field that you can use to augment a failing memory. All VB has is comments embedded in the code. Although again, a good nomenclature system goes a long way.
In VB, you have to write a script to change the properties of an object based on the value of a variable. In WW, just double click on the object, select the property, and reference a tag. Much less chance of a typo. Much easier to debug.
Making something blink is easy in WW. Much less so in VB.
Most of what it comes down to is a matter of time (and time is money is profits, or the lack thereof). VB takes longer to develop in, is harder to maintain (not that WW is a piece of cake, depending on how "script-happy" the application is), and has a steeper learning curve. Someone with minimal experince can walk up to WW and modify a screen in an hour. Even a good VB programmer is going to need a fair amount of time to figure out how the previous programmer set things up, where his calls are, before being able to make the similar changes.
On the other hand, VB is cheaper (especially if you write your own communicaiton driver). So once you've created one application, a second one adds no additional cost (except that I've yet to see two "identical" systems - there's always some difference between them), whereas you at least have to buy a second licence of WW.