EcoStruxure process expert

[Salah_Mohamed]

What's the difference between AVEVA Plant SCADA and EcoStruxure process Expert ? 

[sumanjithan]

AVEVA Plant SCADA is a Supervisory Control and Data Acquisition (SCADA) software solution for industrial process applications.

And the EcoStruxure Process Expert is a modern, distributed control system designed to reduce resources spent on engineering and commissioning. Designed especially for water, mining, cement, power generation, consumer packaged goods and chemical applications. 

[Salah_Mohamed]

but both are Wonderware based and has same ability and speed of polling tags right ?

[sumanjithan]

Both are not Wonderware based. Looks like you are talking about the Aveva system platform, formally Wonderware.

EcoStruxure Process Expert is not a SCADA, it is a platform that helps the users to create the required tags to communicate control project with Aveva Plant SCADA as well as Aveva System Platform.

[AntonioIacoviello]

in other words, Plant SCADA doesn't have all the functionalities described by @sumanjithan but EPE uses (in a VM environment) PS to build some graphics and some SCADA functionalities.
You can achieve the same as EPE does by using Plant SCADA as well, but you will lose some tools and functionalities.