A little late to this party I must admit, but being an enfp who is married to an entp I felt that I could have some limited insight to the topic. BTW Subbie I agree 100% with the idea that an enfp and an entp seem to NEVER be able to get the others point of view. And ironically enough they are so similar yet approached from a different view, one Ti and one Fi. At least that is how I have seen it to be
I have some thoughts that come from a different angle or point of view here as I look at the idea of being superficial. And one thing I need to say is that it really depends on the individual and their life experiences. I believe that the entp is way more sensitive than they let on to be, I believe that they mask and hide a lot behind that playful spontaneous persona, as do enfps. Yet the difference comes in with the 'F' factor, it is I suppose easier to see an enfp's emotion and therefore chalk their views up to emotions. As the emotions of an enfp are hard to pin down and understand.
I also think that the idea and the role of coming off as superficial is like a security blanket. The desire in these two types to be well liked and loved and please others is very strong, yet it leads to a lot of hurt as others can and do take advantage of it. So I believe that a way to protect themselves is to never really let anyone in, is to never really share who you are there is the constant Ne being pushed yet the real entp or enfp lies in the Ti/Fi personality trait. If you as an individual can over look the idea of them being superficial or acting superficial and stand the test of time you will begin to see who they really are, and I think you would probably be more shocked at who an entp really is as opposed to who an enfp really is.
Just some of my thoughts as I walk through a time in my life of personal growth and discovery.