I've used both.
ECam Level 1 costs more than Mastercam and doesn't even have the capability to do basic indexing or rotary.
ECam does not include solid modeling. It is an add on package with a completely different interface than the Ecam interface. Mastercam will read in a solid model from most any source and you can machine it as a solid, without having to purchase the Solids package. You can do that now with your Mill Level 1. Mastercam solids add-on is less expensive than ECam's modelier.
Mastercams solid modelier is Associative to the geometry and runs in the same interface as the Mastercam Design/Toolpath. But ECams modelier is parametric but is a stand alone program with a different interface from the Design/Toolpath program.
You must buy a cad interface for each different Cad system you plan to import (i.e. Solidworks, Inventor, STEP, ProE, Catia). Only IGES and DXF are standard. Only Catia and Proe are an extra cost in Mastercam. All others are standard.
Maintenance costs more for ECam, on a product that already costs more. So you'll probably be paying about twice what your paying now.
3rd party information on using ECam is hard to find. The books that come with the software are not as clear as you might like them to be.
Strategy Manager is the coolest thing in the world. Your dealer may give you some pre-defined Strategies with your purchase, or he may want to charge you for them. Your initial purchase of Strategy Manager does not include any useful Strategies. There is some documentation, but to develop and learn it yourself will take a little time. When you have them properly defined for your exact requirements, They are very cool.
Are you using the FBM toolpaths in your Mastercam? There's no reason why you cant be reading in a Solid Model now and Quickly creating automated toolpaths with it.
I'm not hard to find if you have more questions.