The View() method can load Partial Views.
Is the difference between View() and PartialView() is that View() can
I think the biggest difference is about the use of the _Layout page:
It's up to a view engine to decide if they want to treat partial views different from regular views.
For example, in the WebFormViewEngine there is no difference.
In the new ASP.NET MVC 3 RazorViewEngine there are some differences. Only regular views will have the "_viewstart.cshtml" pages run because they are meant for things such as setting up layout pages.
If you have Index.aspx and Index.ascx for the same controller having both methods might help disambiguate. But I agree that in general View is more commonly used. And PartialView can also be used to load full views, it's just that it's semantically wrong.