It depends. If you have some transmission lines then you might want a ground plane close to the top layer to minimise track widths for a given impedance. prepreg is usually thinner than core, so you would choose the second option.
Second layer stack up is good in my opinion if you have any impedance controlled lines than put your ground layer close to that layer (either of top or bottom)
The two stack up only differs on its build core or prepreg build. If your concern is impedance controlled lines. the two stack up will have the same result on line width.
But i read somewhere that core build for four layer have better PCB strength (Core in the middle) but i'm not sure if this is true. Anyway you can choose any of the two because this two type are both common but core in the middle is more common for four layer. Hope this helps