To start with, VBScript (the flavour of VB that ScriptEditor is aimed at) is very different to VBA in quite a lot of ways.
For example you cannot declare object types, and you cannot directly create an object such as a ADODB Connection.
VBA:
Dim myObject as ADODB.Connection
set myObject = new ADODB.Connection
VBScript:
dim myObject
set myObject = CreateObject("ADODB.Connection")
Visual studio 6 does have advantages such as being able to easily add code to source safe, but you lose the ease of interacting with your Excel document (Sheet1.Range("rangeName"), etc)
In short, I would stick with the VBA editor built into Excel.