The short answer is yes, the service should be exactly the same. There is still the question of whether they'll activate it tho.
There is a discussion about it in the S4 for Metro same as T-Mobile?
thread you can read through if you like...in fact...I recommend reading through it. The problem is that if anyone has already tried what you want to do, they didn't report back either way.
It seems talking to Metro customer service gets the same "duh" response, as you'll see if you read the thread I posted. I think they understand perfectly but act stupid in this case because they want you to buy their S4 variant. You may get more answers by going to a metro store, they get lots of practice activating phones and should be able to give you a better answer than "duh". Problem is that the phone needs to be disconnected from Tmo completely in order to try to activate it on Metro.
Good Luck and let us know how it goes.