If you're gonna use a compare tool to promote from Dev to Prod, you might as well just give the developers full access to Prod... unless you do a code review of ALL the changes. And, how are you gonna know which changes should be promoted and when?

The best way to do this type of thing is to have a ticketing system that keeps track of the work to be done and each bit of code should be released through a Source Control System with some bit of configuration management so you can rollback if you need to and you know what's going in.

Last folks I know that did a diff and promote spent a day or two fixing their prod system because a developer got ticked off...