It depends, of course. If you are happy with basic widgets like buttons, sliders, text boxes, etc, typically seen with the Nordic and RFdigital examples, then the Simblee for Mobile is pretty easy to set up and 'eliminates' the need to create your own iOS/Android apps to go with it.
If you are looking to create your own characteristic UUIDs or BLE SIG Services defined characteristic UUIDs then the Nordic SDK or MBED is the way to go. Even so, the Simblee QFN module itself is fantastically smaller than anything in existance.
Have fun with whatever approach you pick.