Hi Quehay,
I have written a system in VB6 and Oracle using ODBC and ADO.
I didn't have any particular problems using ADO with Oracle.
My only opinion is that if you are using Oracle as a backend database then I would lean towards VB6, as I find it much easier to use than Access for the development of systems. Don't read into this too much, I have just used VB6 a lot more. I also feel that using Access to manipulate Oracle is not really gaining you much.
However one advantage of using Access is that it gives you the opportunity to create queries and develop a system in which you may be familiar. Using VB6 alone requires a strong knowledge of SQL, as you don't have the backup of GUI query designer.
In short I think it depends on your level of programming. If you have the ability to create systems in VB6, take that route, as I feel that they can be designed to look like a very professional bespoke package with relative ease. I am sure that you can do the same with Access, but it might take longer.
N2ckb