If I give Umbacano the Nenalata one, will I get to keep the other one/both? I did it the other way around, he dies but I got the worse of the two only.

for people who doesn't know what he's talking about
http://www.uesp.net/wiki/Oblivion:Secrets_of_the_Ayleids

anyway, i can offer no help. never done any quest of umbacano

Sorry, I always gave the crown of Lindai to Umbacano and after his death I took the broken crown but could not repair it. I never took the Nenalata crown from Herminia Cinna.

If you give him the crown of Nenatala, you get to keep both and use them (properly). I played it again from an earlier save, Claude Maric doesn't even get suspicious saying "How could he have miscalculated like this", he just says we both fell in a trap etc.

Thanks for the replies.