Agatha Christie no Meitantei Poirot to Marple

Agatha Christie work is mentioned sometimes by Conan and others in the show. Many a mystery story has found inspiration in her work. 

"Truth will smile upon me." VS "There is always one truth!" Both are mysteries, both have nods to classic mystery cases of Christie, Conan Doyle, etc. If you are a fan of mysteries of one, I think you'd enjoy the other. In terms of quality, I'd say DC is better and more original (and less derivative since ACnMPtM is based much more on the books), but mystery buffs like myself would likely enjoy both I think. Oh, one small difference is that ACnMPtM focuses on two detectives Poirot and Marple whereas Conan is the clear main focal detective in DC (though there are others too like Heiji/Akai/etc) 

both about young people who involve in solving mystery. 

Case closed type just like Conan but instead of having a little boy, you have a girl working with either Poirot or miss Marple. The style of the episodes is similar as well.  

both anime are about girl who get into mystery cases.  

Looking for a detective story? Check this out.