I would get the 4#6s becoz it has 3 axis gyro , more stable and can be mod to flybarless. and almost the same price but it is a little bigger than the CB100.
4#3b is also a 4ch heli and has same size of the Cb100 but the flybar design is different (90 degree vs 45 degree of the CB100) that make it very responsive. I have CB100 and fly everyday indoor and get boring now becoz it is too stable ......