What is better? Single Sided vs. Double Sided DIMM?

Hi out there,

I am into fixing an old PC to give it to a friend (Fujitsu-Siemens, PIII, ATX, D1107)and I am about to buy a 256MB-(168pin,PC133, CL3).
Could anyone pls tell me what is better a single sided DIMM or a double sided?

Thanks

Callie