One large group policy vs many small group polices

This is a question on best practices.  I want to know which works better for system speed, one or two large group policies or many, like over 10 smaller group polices that would be targeted to specific ou's and groups?

I am looking for overall login speed.  We are revising what we have and trying to decide which is better.  From an administration point of view it seems that the many smaller polices will make it clearer which policy we need to go into to adjust settings.  We are concerned that all the extra policies will increase login time.  We are looking to go from 2 large group polices to about 10 to 15 smaller ones.

Breaking out settings for particular systems like an SCCM policy, a network policy, a security policy.  Where all of these settings we in a default policy before.

I am looking for an explanation of why one way is better than the other.  Preferably with some industry documentation to back up the statement.

Thanks