Sorry to be a proxy again, but this simply can't be put any better than this article I ran into, and this is something every SharePoint developer, project manager, customizer etc. should read and know and apply in SharePoint projects:
It is always the better practise to use a WSP to deploy stuff to SharePoint, even though I too tend to write about the quick and dirty solutions every now and then. Sometimes things need to get done even thought there isn't a developer resource available. Just keep this in mind: solutions rule!