User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-95.112.225.227-20150909071814/@comment-24834479-20150912012332

Castiel certainly seemed stronger, but he could have just been more show off-ish. I believe that Gadreel said the tablet gave Metatron powers equivalent to God, so I would say that Metatron was stronger, but just didn't use he power much.