Another group people should check out is Giving What We Can, which combines tithing with cost-effectiveness analysis, focusing on health charities at the moment. GWWC was founded by Toby Ord, who used to comment here Some charities appear highly on both GWWC and GW's recommendations (Stop TB partnership and Against Malaria Foundation) but they do disagree on some. There are discussions between Will Crouch (of GWWC) and Holden (of GW) in the comments here and here.

Points of disagreement between the two seem to include the usefulness of DALYs (Disability Adjusted Life Years) as a metric (see the first link) and the focus on openness; GW seems to basically assume charities are guilty of inefficiency until proven otherwise, where GWWC basically assumes they're average for their field.

Unfortunately Mandatory but Probably Unnecessary Disclaimer: While obviously not an employee, and nor a pledgee, I have some connection with GWWC. All comments here represent my own views, should not be construed as representing GWWC, etc. etc.