Single sided has the chips on one side of the circuit board only.
Strangly enough double sided has the chips on both sides.
I have seen some MOBO's that can only use one or the other, so the first thing i would do if find out if this restriction applies to you. if you post you MOBO type someone is bound to know.
As for better or not, i am sure someone else can answer that, as i havn't got a clue!