Oracle vs SQL Server

I'm working in an envirnoment using access/97 to the Max., 50+ users accessing 30+ databases on a NT network. It works, but need the handle double, triple or more users within the coming year! I'm thinking about moving to a Oracle or SQL server(MS) system. We using visual basic 6.0, any suggestions and information on the best possible solution for our company!

Note: On the web and on the Data servers web sites, seem to be quite biased on comparing Oracle vs SQL server?

ANy hints or good sites would be great!
Thanks!
Dean Reedy