Hi @Anonymous,
Thank you for visiting Autodesk Forum and your question.
It is hard to tell you a comparison at once but you will be getting familiar with the products if you take a look at the links below.
I just captured some information that you might be interested from the websites. Please refer to the below.


What is AutoCAD MEP :
https://www.autodesk.com/compare/autocad-mep-vs-autocad
What is Fabrication MEP :
https://www.autodesk.com/products/fabrication-products/features
What is Revit MEP :
https://www.autodesk.com/products/revit-family/mep
If you are interested in publishing a drawing for construction, then AutoCAD MEP will be suitable for you.
If you want to coordinate with other trade or order for real fabrication, then Fabrication MEP or Revit MEP will be good for you.
I am not sure what you want exactly but this is my best that I can give you at the moment.
Please feel free to reply, I will be more than happy to assist you.
Thank you for contacting us again. Have a great day!
Best regards,
CH
Chonghyuk Lee
Product Support Specialist

Chonghyuk Lee