4S1P is made up of 4 cells.
4S2P is made up of 8 cells.
From a probability point of view the fewer cells you have making up your battery, the fewer things you have to go wrong.
But even if you order the 4S1P, you might actually get sent a 4S2P. Hobbyking are a bit like that, and that happened to me, and from the feedback has happened to others. Then you have to ask yourself if you want to go through the pain of sending it back - I just kept mine.
Batteries need a bit of TLC if you want long service from them, i.e. protect them from physical shock, don’t let them get too hot or too cold, always balance charge them, don’t overcharge or over discharge them, regularly check the cell impedance if you have the capability to do so.
In operation both banks will appear and work the same.