UNI Attributes (MEF 10.2) are characteristics of the UNI itself and are applied to all services on the UNI. An example is the Physical Layer Service Attribute. If the UNI is a 100Mbps Full Duplex Ethernet, then that is what the services see.
EVC per UNI attributes
EVC per UNI Attributes (MEF 10.2 and MEF 10.3) are EVC attributes that are associated with the specific UNI and can be different on other UNIs within the EVC. An example is the Ingress Bandwidth Profile attribute. Each UNI in an EVC can have different policing values.
EVC Attributes are attributes that describe the EVC itself. They apply to the EVC across the entire carrier network. An example is the EVC Connection Type Attribute. If the EVC is defined as point-to-point, then it must be that way across the whole network.
MEF 6.x defines six Carrier Ethernet Service types, three private service types and three virtual private service types, by constraining the values in each of the three sets of generic attributes to an appropriate set of values. For example, an Ethernet Private Line service must have (note that these are just a sample, there are several other attributes):
UNI Physical Layer MUST BE 10 or 100 or 1000 or 1000Mbps Ethernet, Full Duplex only