hay ill defend the tf-11 cause its an awsome gun.
though i beleve its against rules to share sites. I got mine at the price of 130.00$ plus shipping.
Even though the cost of C02 may more than charging a battery it costs the price of a mag to fix the gun if it breaks (mag is what runs the gun) where as the mp7 if you don't put in the battery in properly you can bend the connecters wich is a pain.
I know theres mp7 lovers but theres only 1 size of battery wich means you'll need 2 at least if your planning on gaming down the line.
Check out my review
but i would actualy spend the 300$ or whatever "Funds" you have on gear first.
good luck and i hope you enjoy what you buy