Pros and Cons of web services vs. classes

I am designing an ASP.NET application that is using a mixture of web services and classes. I am using classes that are broken up into tasks that communicate with the database via stored procedures in a data access layer. I'm thinking of using web services to perform some functions, but this may be redundant in others. I thought maybe I would open a discussion about this. For instance, I need to have a login form that will authenticate the user to the database and then return the userdata stored so it can be set in the user's cookie. I've thought up two different ways of handling this: aspx page --> public sub calls web service --> web service calls DAL class and retrieves userdata from db --> webservice returns data This is neat in that I could use the web service to process logins from a variety of sources. But I worry if this is a good scalable solution in the long run. Would it not be better to just: aspx page --> public sub calls DAL class --> DAL class returns userdata What are your thoughts on this? Is it worth the trouble to have a web service handle things or not? Thanks for your ideas.