Hiya,
That is a very subjective question, and really depends on the experience of the techie's that you have and on your servers.
Generally, VB links better into Ansi standard Dbases (such as Sybase) because that uses the same standard language and interfaces as MS-SQL Server (and remember who writes VB!), so it does have a head start that way.
However, if you are moving large amounts of data frequently, Oracle tends to be the slightly better system.
It also depends on the data you are holding, most people I have spoken to will say that Oracle 8i is best if you are storing large amounts of pictures or music type data...
Guess the real answer is there is no answer...it is based on what you want to do, and what system you prefer....
Tim