hasn't it been established that they are exactly the same levels within Circles?

IIRC numerous posters with both cards have said this.

Merrill+3 = Centurion
Merrill+2 = Platinum

edit >>

http://www.flyertalk.com/forum/showp...8&postcount=15
karthik says +3 = Cent, but isn't sure about +2 = Plat

http://www.flyertalk.com/forum/showp...1&postcount=21
isn't clear how sure enclave is on this..

http://www.flyertalk.com/forum/showp...2&postcount=10
Kyle53719 says he is not sure

i think there are more posts.. but they probably use "ML+2" etc.. i might try a google search.

anyway, i stand corrected. your question is a good one, more information from people with both cards would be good.