Using proto generated class in Java class vs defining individual fields separately in Java class

[jainlavina]

I am building a Java thick client library for a gRPC service and wondering whether tha Java request class that this library exposes to the users should inlcude the proto generated class directly vs individually define the request fields separately in the Java class.

For example given
message gRPCUserRequest {
// request fields
}

Should I define Java request class as:
class UserRequest {
gRPCUserRequest request;
}

vs

class UserRequest {
// request fields
}

Is there a downside to exposing proto generate class directly to the users in the client library?