X2 is cause it has CVT Transmission which means runs on belt and it goes around 40-45mph.
Pocket Are you kidding? Pocket bikes are little kiddies toys that you can only ride in private parking lots. Get a dirt bike and do some REAL riding, enjoy some REAL speed and fun! Pocket bikes look...
BMX isn't a brand, it's a type of bicycle. Whether it's best or not depends on what you want to do with it.
If you can find a large enough bike shop, they should carry pocket bikes or at least be able to direct you to a location that does if they do not.
It really depends on what kind of bike you are getting, but normally, a pocket bike is bigger.