Dangerous Dave

Braided hoses will last a lot longer, so in the long run they are the better option to go for. They will improve braking a tiny bit if you have brand new standard hoses at the moment, however, most people fit braided hoses after a long time with standard rubber hoses, it is at this point that you feel the biggest increase in braking performance! Ypu would also feel that increase if you replaced with new rubber hoses too!

Go for the full set, as Chris said you get an increase in feel and locking the back wheel does not become easier it just puts it back to how it was when the bike was brand new (as the brakes should be). Put to much pressure on the pedal and yes it will lock up, it does that too with old rubber hoses its just that to create the same pressure you have to use more lever/pedal travel!