How to compare two SQL Server 2008 configurations
You really just have to get creative.  As we all know, there are many places that settings are stored, depending on what exactly you're looking to compare.  For instance, to compare instance-wide configuration settings, you can simple do an EXCEPT query (you may have to create a linked server, or export/import the data depending on how you want to approach that):

select *
from [YourProdInstance].master.sys.configurations

except

select *
from [YourDevInstance].master.sys.configurations


Use this same type of methodology for all other configuration settings that you will want to compare.


Find the root of the config data
Get both instances' config data in a common place
Write a query that will compare the data (whether it is XML, or not)