I highly recommend the MP7, I have one and I love it. I love the looks, sounds very intimidating, and is definitely more than accurate enough for a sub machine gun. That being said, if you do get it there is one thing i'd warn you about. You may/may not know that the hop up bucking in it is prone to swelling from too much oil, so don't over oil it or you'll have to take the whole thing apart (the first time it is hard, but after that it is easy, though time consuming).
My brother has had his Mp7 for a year. With a lot of hard use, it still works exactly the same as it did when he got it. Honestly it is a great value for the money. Also I have to mention the accuracy of this. My brothers gun is accurate to 30 yds consistently. It's a great gun.